path: root/pango/pango-renderer.c

/* Pango
 * pango-renderer.h: Base class for rendering
 *
 * Copyright (C) 2004 Red Hat, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include <config.h>
#include <stdlib.h>

#include "pango-renderer.h"

#define N_RENDER_PARTS 4

#define IS_VALID_PART(part) ((guint)part < N_RENDER_PARTS)

typedef struct _LineState LineState;
typedef struct _Point Point;

struct _Point
{
  double x, y;
};

struct _LineState
{
  PangoUnderline underline;
  PangoRectangle underline_rect;
  
  gboolean strikethrough;
  PangoRectangle strikethrough_rect;

  int logical_rect_end;
};

struct _PangoRendererPrivate
{
  PangoColor color[N_RENDER_PARTS];
  gboolean color_set[N_RENDER_PARTS];

  LineState *line_state;
};

static void pango_renderer_finalize                     (GObject          *gobject);
static void pango_renderer_default_draw_glyphs          (PangoRenderer    *renderer,
							 PangoFont        *font,
							 PangoGlyphString *glyphs,
							 int               x,
							 int               y);
static void pango_renderer_default_draw_rectangle       (PangoRenderer    *renderer,
							 PangoRenderPart   part,
							 int               x,
							 int               y,
							 int               width,
							 int               height);
static void pango_renderer_default_draw_error_underline (PangoRenderer    *renderer,
							 int               x,
							 int               y,
							 int               width,
							 int               height);
static void pango_renderer_default_prepare_run          (PangoRenderer    *renderer,
							 PangoLayoutRun   *run);

static void pango_renderer_prepare_run (PangoRenderer  *renderer,
					PangoLayoutRun *run);

static void
to_device (PangoMatrix *matrix,
	   double       x,
	   double       y,
	   Point       *result)
{
  if (matrix)
    {
      result->x = (x * matrix->xx + y * matrix->xy) / PANGO_SCALE + matrix->x0;
      result->y = (x * matrix->yx + y * matrix->yy) / PANGO_SCALE + matrix->y0;
    }
  else
    {
      result->x = x / PANGO_SCALE;
      result->y = y / PANGO_SCALE;
    }
}

G_DEFINE_ABSTRACT_TYPE (PangoRenderer, pango_renderer, G_TYPE_OBJECT)

static void
pango_renderer_class_init (PangoRendererClass *klass)
{
  GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
  
  klass->draw_glyphs = pango_renderer_default_draw_glyphs;
  klass->draw_rectangle = pango_renderer_default_draw_rectangle;
  klass->draw_error_underline = pango_renderer_default_draw_error_underline;
  klass->prepare_run = pango_renderer_default_prepare_run;

  gobject_class->finalize = pango_renderer_finalize;

  g_type_class_add_private (gobject_class, sizeof (PangoRendererPrivate));
}

static void
pango_renderer_init (PangoRenderer *renderer)
{
  renderer->priv = G_TYPE_INSTANCE_GET_PRIVATE (renderer,
						PANGO_TYPE_RENDERER,
						PangoRendererPrivate);
  renderer->matrix = NULL;
}

static void
pango_renderer_finalize (GObject *gobject)
{
  PangoRenderer *renderer = PANGO_RENDERER (gobject);
  
  if (renderer->matrix)
    pango_matrix_free (renderer->matrix);
}

/**
 * pango_renderer_draw_layout:
 * @renderer: a #PangoRenderer
 * @layout: a #PangoLayout
 * @x: X position of left edge of baseline, in user space coordinates
 *   in Pango units.
 * @y: Y position of left edge of baseline, in user space coordinates
 *    in Pango units.
 *
 * Draws @layout with the specified #PangoRenderer.
 *
 * Since: 1.8
 **/
void
pango_renderer_draw_layout (PangoRenderer    *renderer,
			    PangoLayout      *layout,
			    int               x,
			    int               y)
{
  PangoLayoutIter *iter;
  
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  g_return_if_fail (PANGO_IS_LAYOUT (layout));

  /* We only change the matrix if the renderer isn't already
   * active.
   */
  if (!renderer->active_count)
    {
      PangoContext *context = pango_layout_get_context (layout);
      pango_renderer_set_matrix (renderer,
				 pango_context_get_matrix (context));
    }
  
  pango_renderer_activate (renderer);

  iter = pango_layout_get_iter (layout);

  do
    {
      PangoRectangle   logical_rect;
      PangoLayoutLine *line;
      int              baseline;
      
      line = pango_layout_iter_get_line (iter);
      
      pango_layout_iter_get_line_extents (iter, NULL, &logical_rect);
      baseline = pango_layout_iter_get_baseline (iter);

      pango_renderer_draw_layout_line (renderer,
				       line,
				       x + logical_rect.x,
				       y + baseline);
    }
  while (pango_layout_iter_next_line (iter));

  pango_layout_iter_free (iter);
  
  pango_renderer_deactivate (renderer);
}

static void
draw_underline (PangoRenderer *renderer,
		LineState     *state)
{
  PangoRectangle *rect = &state->underline_rect;
  PangoUnderline underline = state->underline;
  
  state->underline = PANGO_UNDERLINE_NONE;
  
  switch (underline)
    {
    case PANGO_UNDERLINE_NONE:
      break;
    case PANGO_UNDERLINE_DOUBLE:
      pango_renderer_draw_rectangle (renderer,
				     PANGO_RENDER_PART_UNDERLINE,
				     rect->x,
				     rect->y + 2 * rect->height,
				     rect->width,
				     rect->height);
      /* Fall through */
    case PANGO_UNDERLINE_SINGLE:
    case PANGO_UNDERLINE_LOW:
      pango_renderer_draw_rectangle (renderer,
				     PANGO_RENDER_PART_UNDERLINE,
				     rect->x,
				     rect->y,
				     rect->width,
				     rect->height);
      break;
    case PANGO_UNDERLINE_ERROR:
      pango_renderer_draw_error_underline (renderer,
					   rect->x,
					   rect->y,
					   rect->width,
					   3 * rect->height);
      break;
    }
}

static void
draw_strikethrough (PangoRenderer *renderer,
		    LineState     *state)
{
  PangoRectangle *rect = &state->strikethrough_rect;
  gboolean strikethrough = state->strikethrough;

  state->strikethrough = FALSE;
  
  if (strikethrough)
    pango_renderer_draw_rectangle (renderer,
				   PANGO_RENDER_PART_STRIKETHROUGH,
				   rect->x,
				   rect->y,
				   rect->width,
				   rect->height);
}

static void
handle_line_state_change (PangoRenderer  *renderer,
			  PangoRenderPart part)
{
  LineState *state = renderer->priv->line_state;
  if (!state)
    return;
    
  if (part == PANGO_RENDER_PART_UNDERLINE &&
      state->underline != PANGO_UNDERLINE_NONE)
    {
      PangoRectangle *rect = &state->underline_rect;
      
      rect->width = state->logical_rect_end - rect->x;
      draw_underline (renderer, state);
      state->underline = renderer->underline;
      rect->x = state->logical_rect_end;
      rect->width = 0;
    }

  if (part == PANGO_RENDER_PART_STRIKETHROUGH &&
      state->strikethrough)
    {
      PangoRectangle *rect = &state->strikethrough_rect;

      rect->width = state->logical_rect_end - rect->x;
      draw_strikethrough (renderer, state);
      state->strikethrough = renderer->strikethrough;
      rect->x = state->logical_rect_end;
      rect->width = 0;
    }
}

static void
add_underline (PangoRenderer    *renderer,
	       LineState        *state,
	       PangoFontMetrics *metrics,
	       int               base_x,
	       int               base_y,
	       PangoRectangle   *ink_rect,
	       PangoRectangle   *logical_rect)
{
  PangoRectangle *current_rect = &state->underline_rect;
  PangoRectangle new_rect;
      
  int underline_thickness = pango_font_metrics_get_underline_thickness (metrics);
  int underline_position = pango_font_metrics_get_underline_position (metrics);

  new_rect.x = base_x + logical_rect->x;
  new_rect.width = logical_rect->width;
  new_rect.height = underline_thickness;
  new_rect.y = base_y;
  
  switch (renderer->underline)
    {
    case PANGO_UNDERLINE_NONE:
      g_assert_not_reached ();
      break;
    case PANGO_UNDERLINE_SINGLE:
    case PANGO_UNDERLINE_DOUBLE:
    case PANGO_UNDERLINE_ERROR:
      new_rect.y -= underline_position;
      break;
    case PANGO_UNDERLINE_LOW:
      new_rect.y += ink_rect->y + ink_rect->height + underline_thickness;
      break;
    }
  
  if (renderer->underline == state->underline &&
      new_rect.y == current_rect->y &&
      new_rect.height == current_rect->height)
    {
      current_rect->width = new_rect.x + new_rect.width - current_rect->x;
    }
  else
    {
      draw_underline (renderer, state);
      
      *current_rect = new_rect;
      state->underline = renderer->underline;
    }
}

static void
add_strikethrough (PangoRenderer    *renderer,
		   LineState        *state,
		   PangoFontMetrics *metrics,
		   int               base_x,
		   int               base_y,
		   PangoRectangle   *ink_rect,
		   PangoRectangle   *logical_rect)
{
  PangoRectangle *current_rect = &state->strikethrough_rect;
  PangoRectangle new_rect;
  
  int strikethrough_thickness = pango_font_metrics_get_strikethrough_thickness (metrics);
  int strikethrough_position = pango_font_metrics_get_strikethrough_position (metrics);
  
  new_rect.x = base_x + logical_rect->x;
  new_rect.width = logical_rect->width;
  new_rect.y = base_y - strikethrough_position;
  new_rect.height = strikethrough_thickness;
  
  if (state->strikethrough &&
      new_rect.y == current_rect->y &&
      new_rect.height == current_rect->height)
    {
      current_rect->width = new_rect.x + new_rect.width - current_rect->x;
    }
  else
    {
      draw_strikethrough (renderer, state);
      
      *current_rect = new_rect;
      state->strikethrough = TRUE;
    }
}

static void
get_item_properties (PangoItem       *item,
		     gint            *rise,
		     PangoAttrShape **shape_attr)
{
  GSList *l;

  if (rise)
    *rise = 0;

  if (shape_attr)
    *shape_attr = NULL;

  for (l = item->analysis.extra_attrs; l; l = l->next)
    {
      PangoAttribute *attr = l->data;

      switch (attr->klass->type)
	{
	case PANGO_ATTR_SHAPE:
	  if (shape_attr)
	    *shape_attr = (PangoAttrShape *)attr;
	  break;

        case PANGO_ATTR_RISE:
          if (rise)
            *rise = ((PangoAttrInt *)attr)->value;
          break;

	default:
	  break;
	}
    }
}

static void
draw_shaped_glyphs (PangoRenderer    *renderer,
		    PangoGlyphString *glyphs,
		    PangoAttrShape   *attr,
		    int               x,
		    int               y)
{
  PangoRendererClass *class = PANGO_RENDERER_GET_CLASS (renderer);
  int i;

  if (!class->draw_shape)
    return;

  for (i = 0; i < glyphs->num_glyphs; i++)
    {
      PangoGlyphInfo *gi = &glyphs->glyphs[i];

      class->draw_shape (renderer, attr, x, y);

      x += gi->geometry.width;
    }
}

/**
 * pango_renderer_draw_layout_line:
 * @renderer: a #PangoRenderer
 * @line: a #PangoLayoutLine
 * @x: X position of left edge of baseline, in user space coordinates
 *   in Pango units.
 * @y: Y position of left edge of baseline, in user space coordinates
 *    in Pango units.
 *
 * Draws @line with the specified #PangoRenderer.
 *
 * Since: 1.8
 **/
void
pango_renderer_draw_layout_line (PangoRenderer    *renderer,
				 PangoLayoutLine  *line,
				 int               x,
				 int               y)
{
  int x_off = 0;
  int glyph_string_width;
  LineState state;
  GSList *l;
  gboolean got_overall = FALSE;
  PangoRectangle overall_rect;
  
  g_return_if_fail (PANGO_IS_RENDERER (renderer));

  /* We only change the matrix if the renderer isn't already
   * active.
   */
  if (!renderer->active_count)
    {
      PangoContext *context = pango_layout_get_context (line->layout);
      pango_renderer_set_matrix (renderer,
				 pango_context_get_matrix (context));
    }

  pango_renderer_activate (renderer);

  renderer->priv->line_state = &state;

  state.underline = PANGO_UNDERLINE_NONE;
  state.strikethrough = FALSE;

  for (l = line->runs; l; l = l->next)
    {
      PangoFontMetrics *metrics;
      gint rise;
      PangoLayoutRun *run = l->data;
      PangoAttrShape *shape_attr;
      PangoRectangle ink_rect, *ink = NULL;
      PangoRectangle logical_rect, *logical = NULL;

      if (run->item->analysis.centered_baseline)
        logical = &logical_rect;

      pango_renderer_prepare_run (renderer, run);
      
      get_item_properties (run->item, &rise, &shape_attr);

      if (shape_attr)
	{
	  ink_rect = shape_attr->ink_rect;
	  logical_rect = shape_attr->logical_rect;
	  ink = &ink_rect;
	  logical = &logical_rect;
	  glyph_string_width = shape_attr->logical_rect.width;
	}
      else
	{
	  if (renderer->underline != PANGO_UNDERLINE_NONE ||
	      renderer->strikethrough)
	    {
	      ink = &ink_rect;
	      logical = &logical_rect;
	    }
	  if (G_UNLIKELY (ink || logical))
	    pango_glyph_string_extents (run->glyphs, run->item->analysis.font,
					ink, logical);
	  if (logical)
	    glyph_string_width = logical_rect.width;
	  else
	    glyph_string_width = pango_glyph_string_get_width (run->glyphs);
	}

      state.logical_rect_end = x + x_off + glyph_string_width;

      if (run->item->analysis.centered_baseline)
        rise += logical_rect.y + logical_rect.height / 2;


      if (renderer->priv->color_set[PANGO_RENDER_PART_BACKGROUND])
	{
	  if (!got_overall)
	    {
	      pango_layout_line_get_extents (line, NULL, &overall_rect);
	      got_overall = TRUE;
	    }
	  
	  pango_renderer_draw_rectangle (renderer,
					 PANGO_RENDER_PART_BACKGROUND,
					 x + x_off,
					 y - rise + overall_rect.y,
					 glyph_string_width,
					 overall_rect.height);
	}

      if (shape_attr)
	{
	  draw_shaped_glyphs (renderer, run->glyphs, shape_attr, x + x_off, y - rise);
	}
      else
	{
	  pango_renderer_draw_glyphs (renderer,
				      run->item->analysis.font, run->glyphs,
				      x + x_off, y - rise);
	}

      if (renderer->underline != PANGO_UNDERLINE_NONE ||
	  renderer->strikethrough)
	{
	  metrics = pango_font_get_metrics (run->item->analysis.font,
					    run->item->analysis.language);
	  
	  if (renderer->underline != PANGO_UNDERLINE_NONE)
	    add_underline (renderer, &state,metrics,
			   x + x_off, y - rise,
			   ink, logical);
	  
	  if (renderer->strikethrough)
	    add_strikethrough (renderer, &state, metrics,
			       x + x_off, y - rise,
			       ink, logical);
	  
	  pango_font_metrics_unref (metrics);
	}

      if (renderer->underline == PANGO_UNDERLINE_NONE &&
	  state.underline != PANGO_UNDERLINE_NONE)
	draw_underline (renderer, &state);

      if (!renderer->strikethrough && state.strikethrough)
	draw_strikethrough (renderer, &state);

      x_off += glyph_string_width;
    }

  /* Finish off any remaining underlines
   */
  draw_underline (renderer, &state);
  draw_strikethrough (renderer, &state);

  renderer->priv->line_state = NULL;
  
  pango_renderer_deactivate (renderer);
}

/**
 * pango_renderer_draw_glyphs:
 * @renderer: a #PangoRenderer
 * @font: a #PangoFont
 * @glyphs: a #PangoGlyphString
 * @x: X position of left edge of baseline, in user space coordinates
 *   in Pango units.
 * @y: Y position of left edge of baseline, in user space coordinates
 *    in Pango units.
 *
 * Draws the glyphs in @glyphs with the specified #PangoRenderer.
 *
 * Since: 1.8
 **/
void
pango_renderer_draw_glyphs (PangoRenderer    *renderer,
			    PangoFont        *font,
			    PangoGlyphString *glyphs,
			    int               x,
			    int               y)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  
  pango_renderer_activate (renderer);

  PANGO_RENDERER_GET_CLASS (renderer)->draw_glyphs (renderer, font, glyphs, x, y);
  
  pango_renderer_deactivate (renderer);
}

static void
pango_renderer_default_draw_glyphs (PangoRenderer    *renderer,
				    PangoFont        *font,
				    PangoGlyphString *glyphs,
				    int               x,
				    int               y)
{
  int i;
  int x_position = 0;

  for (i = 0; i < glyphs->num_glyphs; i++)
    {
      PangoGlyphInfo *gi = &glyphs->glyphs[i];
      Point p;
      
      to_device (renderer->matrix,
		 x + x_position + gi->geometry.x_offset,
		 y +              gi->geometry.y_offset,
		 &p);

      pango_renderer_draw_glyph (renderer, font, gi->glyph, p.x, p.y);

      x_position += gi->geometry.width;
    }
}

/**
 * pango_renderer_draw_rectangle:
 * @renderer: a #PangoRenderer
 * @part: type of object this rectangle is part of
 * @x: X position at which to draw rectangle, in user space coordinates in Pango units
 * @y: Y position at which to draw rectangle, in user space coordinates in Pango units
 * @width: width of rectangle in Pango units in user space coordinates
 * @height: height of rectangle in Pango units in user space coordinates
 *
 * Draws an axis-aligned rectangle in user space coordinates with the
 * specified #PangoRenderer.
 *
 * This should be called while @renderer is already active.  Use
 * pango_renderer_activate() to activate a renderer.
 *
 * Since: 1.8
 **/
void
pango_renderer_draw_rectangle (PangoRenderer   *renderer,
			       PangoRenderPart  part,
			       int              x,
			       int              y,
			       int              width,
			       int              height)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  g_return_if_fail (IS_VALID_PART (part));
  g_return_if_fail (renderer->active_count > 0);
  
  PANGO_RENDERER_GET_CLASS (renderer)->draw_rectangle (renderer, part, x, y, width, height);
}

static int
compare_points (const void *a,
		const void *b)
{
  const Point *pa = a;
  const Point *pb = b;

  if (pa->y < pb->y)
    return -1;
  else if (pa->y > pb->y)
    return 1;
  else if (pa->x < pb->x)
    return -1;
  else if (pa->x > pb->x)
    return 1;
  else
    return 0;
}

static void
draw_rectangle (PangoRenderer   *renderer,
		PangoMatrix     *matrix,
		PangoRenderPart  part,
		int              x,
		int              y,
		int              width,
		int              height)
{
  Point points[4];

  /* Convert the points to device coordinates, and sort
   * in ascending Y order. (Ordering by X for ties)
   */
  to_device (matrix, x, y, &points[0]);
  to_device (matrix, x + width, y, &points[1]);
  to_device (matrix, x, y + height, &points[2]);
  to_device (matrix, x + width, y + height, &points[3]);

  qsort (points, 4, sizeof (Point), compare_points);

  /* There are essentially three cases. (There is a fourth
   * case where trapezoid B is degenerate and we just have
   * two triangles, but we don't need to handle it separately.)
   *
   *     1            2             3
   *
   *     ______       /\           /\
   *    /     /      /A \         /A \
   *   /  B  /      /____\       /____\
   *  /_____/      /  B  /       \  B  \
   *              /_____/         \_____\
   *              \ C  /           \ C  /
   *               \  /             \  /
   *                \/               \/
   */
  if (points[0].y == points[1].y)
    {
     /* Case 1 (pure shear) */
      pango_renderer_draw_trapezoid (renderer, part,                                      /* B */
				     points[0].y, points[0].x, points[1].x,
				     points[2].y, points[2].x, points[3].x);
    }
  else if (points[1].x < points[2].x)
    {
      /* Case 2 */
      double tmp_width = ((points[2].x - points[0].x) * (points[1].y - points[0].y)) / (points[2].y - points[0].y);
      double base_width = tmp_width + points[0].x - points[1].x;

      pango_renderer_draw_trapezoid (renderer, part,                                      /* A */
				     points[0].y, points[0].x, points[0].x,
				     points[1].y, points[1].x, points[1].x + base_width);
      pango_renderer_draw_trapezoid (renderer, part,                                      /* B */
				     points[1].y, points[1].x, points[1].x + base_width,
				     points[2].y, points[2].x - base_width, points[2].x);
      pango_renderer_draw_trapezoid (renderer, part,                                      /* C */
				     points[2].y, points[2].x - base_width, points[2].x, 
				     points[3].y, points[3].x, points[3].x);
    }
  else
    {
      /* case 3 */
      double tmp_width = ((points[0].x - points[2].x) * (points[1].y - points[0].y)) / (points[2].y - points[0].y);
      double base_width = tmp_width + points[1].x - points[0].x;

      pango_renderer_draw_trapezoid (renderer, part,                                     /* A */
				     points[0].y, points[0].x, points[0].x,
				     points[1].y,  points[1].x - base_width, points[1].x);
      pango_renderer_draw_trapezoid (renderer, part,                                     /* B */
				     points[1].y, points[1].x - base_width, points[1].x,
				     points[2].y, points[2].x, points[2].x + base_width);
      pango_renderer_draw_trapezoid (renderer, part,                                     /* C */
				     points[2].y, points[2].x, points[2].x + base_width, 
				     points[3].y, points[3].x, points[3].x);
    }
}

static void
pango_renderer_default_draw_rectangle (PangoRenderer  *renderer,
				       PangoRenderPart part,
				       int             x,
				       int             y,
				       int             width,
				       int             height)
{
  draw_rectangle (renderer, renderer->matrix, part, x, y, width, height);
}

/**
 * pango_renderer_draw_error_underline:
 * @renderer: a #PangoRenderer
 * @x: X coordinate of underline, in Pango units in user coordinate system
 * @y: Y coordinate of underline, in Pango units in user coordinate system
 * @width: width of underline, in Pango units in user coordinate system
 * @height: height of underline, in Pango units in user coordinate system
 *
 * Draw a squiggly line that approximately covers the given rectangle
 * in the style of an underline used to indicate a spelling error.
 * (The width of the underline is rounded to an integer number
 * of up/down segments and the resulting rectangle is centered
 * in the original rectangle)
 *
 * This should be called while @renderer is already active.  Use
 * pango_renderer_activate() to activate a renderer.
 *
 * Since: 1.8
 **/
void
pango_renderer_draw_error_underline (PangoRenderer *renderer,
				     int            x,
				     int            y,
				     int            width,
				     int            height)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  g_return_if_fail (renderer->active_count > 0);
  
  PANGO_RENDERER_GET_CLASS (renderer)->draw_error_underline (renderer, x, y, width, height);
}

/* We are drawing an error underline that looks like one of:
 *
 *  /\      /\      /\        /\      /\               -
 * /  \    /  \    /  \      /  \    /  \              |
 * \   \  /\   \  /   /      \   \  /\   \             |
 *  \   \/B \   \/ C /        \   \/B \   \            | height = HEIGHT_SQUARES * square
 *   \ A \  /\ A \  /          \ A \  /\ A \           | 
 *    \   \/  \   \/            \   \/  \   \          |
 *     \  /    \  /              \  /    \  /          |
 *      \/      \/                \/      \/           -
 *      |---|
 *    unit_width = (HEIGHT_SQUARES - 1) * square
 *
 * To do this conveniently, we work in a coordinate system where A,B,C
 * are axis aligned rectangles. (If fonts were square, the diagrams
 * would be clearer)
 *
 *             (0,0)    
 *              /\      /\        
 *             /  \    /  \      
 *            /\  /\  /\  /      
 *           /  \/  \/  \/       
 *          /    \  /\  /        
 *      Y axis    \/  \/         
 *                 \  /\          
 *                  \/  \         
 *                       \ X axis
 *
 * Note that the long side in this coordinate system is HEIGHT_SQUARES + 1
 * units long
 *
 * The diagrams above are shown with HEIGHT_SQUARES an integer, but
 * that is actually incidental; the value 2.5 below seems better than
 * either HEIGHT_SQUARES=3 (a little long and skinny) or
 * HEIGHT_SQUARES=2 (a bit short and stubby)
 */
 
#define HEIGHT_SQUARES 2.5

static void
get_total_matrix (PangoMatrix       *total,
		  const PangoMatrix *global,
		  int                x,
		  int                y,
		  int                square)
{
  PangoMatrix local;
  gdouble scale = 0.5 * square;

  /* The local matrix translates from the axis aligned coordinate system
   * to the original user space coordinate system.
   */
  local.xx = scale;
  local.xy = - scale;
  local.yx = scale;
  local.yy = scale;
  local.x0 = 0;
  local.y0 = 0;

  *total = *global;
  pango_matrix_concat (total, &local);

  total->x0 = (global->xx * x + global->xy * y) / PANGO_SCALE + global->x0;
  total->y0 = (global->yx * x + global->yy * y) / PANGO_SCALE + global->y0;
}

static void
pango_renderer_default_draw_error_underline (PangoRenderer *renderer,
					     int            x,
					     int            y,
					     int            width,
					     int            height)
{
  int square = height / HEIGHT_SQUARES;
  int unit_width = (HEIGHT_SQUARES - 1) * square;
  int width_units = (width + unit_width / 2) / unit_width;
  static const PangoMatrix identity = PANGO_MATRIX_INIT;
  const PangoMatrix *matrix;

  x += (width - width_units * unit_width) / 2;
  width = width_units * unit_width;

  if (renderer->matrix)
    matrix = renderer->matrix;
  else
    matrix = &identity;

  while (TRUE)
    {
      PangoMatrix total;
      get_total_matrix (&total, matrix, x, y, square);

      draw_rectangle (renderer, &total, PANGO_RENDER_PART_UNDERLINE, /* A */
		      0,                      0,
		      HEIGHT_SQUARES * 2 - 1, 1);

      if (width_units > 2)
	{
	  draw_rectangle (renderer, &total, PANGO_RENDER_PART_UNDERLINE, /* B */
			  HEIGHT_SQUARES * 2 - 2, - (HEIGHT_SQUARES * 2 - 3),
			  1,                      HEIGHT_SQUARES * 2 - 3);
	  width_units -= 2;
	  x += unit_width * 2;
	}
      else if (width_units == 2)
	{
	  draw_rectangle (renderer, &total, PANGO_RENDER_PART_UNDERLINE, /* C */
			  HEIGHT_SQUARES * 2 - 2, - (HEIGHT_SQUARES * 2 - 2),
			  1,                      HEIGHT_SQUARES * 2 - 2);
	  break;
	}
      else
	break;
    }
}

/**
 * pango_renderer_draw_trapezoid:
 * @renderer: a #PangoRenderer
 * @part: type of object this trapezoid is part of
 * @y1_: Y coordinate of top of trapezoid
 * @x11: X coordinate of left end of top of trapezoid
 * @x21: X coordinate of right end of top of trapezoid
 * @y2: Y coordinate of bottom of trapezoid
 * @x12: X coordinate of left end of bottom of trapezoid
 * @x22: X coordinate of right end of bottom of trapezoid
 * 
 * Draws a trapezoid with the parallel sides aligned with the X axis
 * using the given #PangoRenderer; coordinates are in device space.
 *
 * Since: 1.8
 **/
void
pango_renderer_draw_trapezoid (PangoRenderer  *renderer,
			       PangoRenderPart part,
			       double          y1_,
			       double          x11,
			       double          x21,
			       double          y2,
			       double          x12,
			       double          x22)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  g_return_if_fail (renderer->active_count > 0);
  
  if (PANGO_RENDERER_GET_CLASS (renderer)->draw_trapezoid)
    PANGO_RENDERER_GET_CLASS (renderer)->draw_trapezoid (renderer, part,
							 y1_, x11, x21,
							 y2, x12, x22);
}

/**
 * pango_renderer_draw_glyph:
 * @renderer: a #PangoRenderer
 * @font: a #PangoFont
 * @glyph: the glyph index of a single glyph
 * @x: X coordinate of left edge of baseline of glyph
 * @y: Y coordinate of left edge of baseline of glyph
 * 
 * Draws a single glyph with coordinates in device space.
 *
 * Since: 1.8
 **/
void
pango_renderer_draw_glyph (PangoRenderer *renderer,
			   PangoFont     *font,
			   PangoGlyph     glyph,
			   double         x,
			   double         y)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  g_return_if_fail (renderer->active_count > 0);
	  
  if (glyph == PANGO_GLYPH_EMPTY) /* glyph PANGO_GLYPH_EMPTY never renders */
    return;
  
  if (PANGO_RENDERER_GET_CLASS (renderer)->draw_glyph)
    PANGO_RENDERER_GET_CLASS (renderer)->draw_glyph (renderer, font, glyph, x, y);
}

/**
 * pango_renderer_activate:
 * @renderer: a #PangoRenderer
 * 
 * Does initial setup before rendering operations on @renderer.
 * pango_renderer_deactivate() should be called when done drawing.
 * Calls such as pango_renderer_draw_layout() automatically
 * activate the layout before drawing on it. Calls to
 * pango_renderer_activate() and pango_renderer_deactivate() can
 * be nested and the renderer will only be initialized and
 * deinitialized once.
 *
 * Since: 1.8
 **/
void
pango_renderer_activate (PangoRenderer *renderer)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));

  renderer->active_count++;
  if (renderer->active_count == 1)
    {
      if (PANGO_RENDERER_GET_CLASS (renderer)->begin)
	PANGO_RENDERER_GET_CLASS (renderer)->begin (renderer);
    }
}

/**
 * pango_renderer_deactivate:
 * @renderer: a #PangoRenderer
 * 
 * Cleans up after rendering operations on @renderer. See
 * docs for pango_renderer_activate().
 *
 * Since: 1.8
 **/
void
pango_renderer_deactivate (PangoRenderer *renderer)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  g_return_if_fail (renderer->active_count > 0);
  
  if (renderer->active_count == 1)
    {
      if (PANGO_RENDERER_GET_CLASS (renderer)->end)
	PANGO_RENDERER_GET_CLASS (renderer)->end (renderer);
    }
  renderer->active_count--;
}

/**
 * pango_renderer_set_color:
 * @renderer: a #PangoRenderer
 * @part: the part to change the color of
 * @color: the new color or %NULL to unset the current color
 * 
 * Sets the color for part of the rendering.
 *
 * Since: 1.8
 **/
void
pango_renderer_set_color (PangoRenderer    *renderer,
			  PangoRenderPart   part,
			  const PangoColor *color)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  g_return_if_fail (IS_VALID_PART (part));

  if ((!color && !renderer->priv->color_set[part]) ||
      (color && renderer->priv->color_set[part] &&
       renderer->priv->color[part].red == color->red &&
       renderer->priv->color[part].green == color->green &&
       renderer->priv->color[part].blue == color->blue))
    return;

  pango_renderer_part_changed (renderer, part);
  
  if (color)
    {
      renderer->priv->color_set[part] = TRUE;
      renderer->priv->color[part] = *color;
    }
  else
    {
      renderer->priv->color_set[part] = FALSE;
    }
}

/**
 * pango_renderer_get_color:
 * @renderer: a #PangoRenderer
 * @part: the part to get the color for
 * 
 * Gets the current rendering color for the specified part.
 * 
 * Return value: the color for the specified part, or %NULL
 *  if it hasn't been set and should be inherited from the
 *  environment.
 *
 * Since: 1.8
 **/
PangoColor *
pango_renderer_get_color (PangoRenderer   *renderer,
			  PangoRenderPart  part)
{
  g_return_val_if_fail (PANGO_IS_RENDERER (renderer), NULL);
  g_return_val_if_fail (IS_VALID_PART (part), NULL);
  
  if (renderer->priv->color_set[part])
    return &renderer->priv->color[part];
  else
    return NULL;
}

/**
 * pango_renderer_part_changed:
 * @renderer: a #PangoRenderer
 * @part: the part for which rendering has changed.
 * 
 * Informs Pango that the way that the renderering is done
 * for @part has changed in a way that would prevent multiple
 * pieces being joined together into one drawing call. For
 * instance, if a subclass of #PangoRenderer was to add a stipple
 * option for drawing underlines, it needs to call
 *
 * <informalexample><programlisting>
 * pango_renderer_part_changed (render, PANGO_RENDER_PART_UNDERLINE);
 * </programlisting></informalexample>
 *
 * When the stipple changes or underlines with different stipples
 * might be joined together. Pango automatically calls this for
 * changes to colors. (See pango_renderer_set_color())
 *
 * Since: 1.8
 **/
void
pango_renderer_part_changed (PangoRenderer    *renderer,
			     PangoRenderPart   part)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  g_return_if_fail (IS_VALID_PART (part));
  g_return_if_fail (renderer->active_count > 0);
  
  handle_line_state_change (renderer, part);

  if (PANGO_RENDERER_GET_CLASS (renderer)->part_changed)
    PANGO_RENDERER_GET_CLASS (renderer)->part_changed (renderer, part);
}

/**
 * pango_renderer_prepare_run:
 * @renderer: a #PangoRenderer
 * @run: a #PangoLayoutRun
 * 
 * Set up the state of the PangoRenderer for rendering @run.
 *
 * Since: 1.8
 **/
static void
pango_renderer_prepare_run (PangoRenderer  *renderer,
			    PangoLayoutRun *run)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));
  
  PANGO_RENDERER_GET_CLASS (renderer)->prepare_run (renderer, run);
}

static void
pango_renderer_default_prepare_run (PangoRenderer  *renderer,
				    PangoLayoutRun *run)
{
  PangoColor *fg_color = NULL;
  PangoColor *bg_color = NULL;
  PangoColor *underline_color = NULL;
  PangoColor *strikethrough_color = NULL;
  GSList *l;

  renderer->underline = PANGO_UNDERLINE_NONE;
  renderer->strikethrough = FALSE;

  for (l = run->item->analysis.extra_attrs; l; l = l->next)
    {
      PangoAttribute *attr = l->data;
      
      switch (attr->klass->type)
	{
	case PANGO_ATTR_UNDERLINE:
	  renderer->underline = ((PangoAttrInt *)attr)->value;
	  break;
	  
	case PANGO_ATTR_STRIKETHROUGH:
	  renderer->strikethrough = ((PangoAttrInt *)attr)->value;
	  break;
	  
	case PANGO_ATTR_FOREGROUND:
	  fg_color = &((PangoAttrColor *)attr)->color;
	  break;
	  
	case PANGO_ATTR_BACKGROUND:
	  bg_color = &((PangoAttrColor *)attr)->color;
	  break;
	  
	case PANGO_ATTR_UNDERLINE_COLOR:
	  underline_color = &((PangoAttrColor *)attr)->color;
	  break;
	  
	case PANGO_ATTR_STRIKETHROUGH_COLOR:
	  strikethrough_color = &((PangoAttrColor *)attr)->color;
	  break;
	  
	default:
	  break;
	}
    }

  if (!underline_color)
    underline_color = fg_color;

  if (!strikethrough_color)
    strikethrough_color = fg_color;

  pango_renderer_set_color (renderer, PANGO_RENDER_PART_FOREGROUND, fg_color);
  pango_renderer_set_color (renderer, PANGO_RENDER_PART_BACKGROUND, bg_color);
  pango_renderer_set_color (renderer, PANGO_RENDER_PART_UNDERLINE, underline_color);
  pango_renderer_set_color (renderer, PANGO_RENDER_PART_STRIKETHROUGH, strikethrough_color);
}

/**
 * pango_renderer_set_matrix:
 * @renderer: a #PangoRenderer
 * @matrix: a #PangoMatrix, or %NULL to unset any existing matrix.
 *  (No matrix set is the same as setting the identity matrix.)
 * 
 * Sets the transformation matrix that will be applied when rendering.
 *
 * Since: 1.8
 **/
void
pango_renderer_set_matrix (PangoRenderer     *renderer,
			   const PangoMatrix *matrix)
{
  g_return_if_fail (PANGO_IS_RENDERER (renderer));

  if (renderer->matrix)
    pango_matrix_free (renderer->matrix);
  if (matrix)
    renderer->matrix = pango_matrix_copy (matrix);
  else
    renderer->matrix = NULL;

}

/**
 * pango_renderer_get_matrix:
 * @renderer: a #PangoRenderer
 *
 * Gets the transformation matrix that will be applied when
 * rendering. See pango_renderer_set_matrix().
 *
 * Return value: the matrix, or %NULL if no matrix has been set
 *  (which is the same as the identity matrix). The returned
 *  matrix is owned by Pango and must not be modified or
 *  freed.
 *
 * Since: 1.8
 **/
G_CONST_RETURN PangoMatrix *
pango_renderer_get_matrix (PangoRenderer *renderer)
{
  g_return_val_if_fail (PANGO_IS_RENDERER (renderer), NULL);

  return renderer->matrix;
}