Add support for BGRA glyphs display and scaling

Display is done using an XRender Picture, as XRender
glyphs are incompatible with BGRA rendering due to
their use of the glyph bitmap as a mask.

Scaling is done by averaging all relevant pixel, which gives
much better result than nearest pixel sampling while staying
simple enough and not too computationally expensive.

This enables color emoji rendering support.

Fixes: #6

Signed-off-by: Maxime Coste <mawww@kakoune.org>
Signed-off-by: Thomas E. Dickey <dickey@invisible-island.net>

1 files changed, 56 insertions, 13 deletions

diff --git a/src/xftrender.c b/src/xftrender.c
index aad5431..721cae0 100644
--- a/src/xftrender.c
+++ b/src/xftrender.c
@@ -84,12 +84,14 @@ XftGlyphRender (Display		*dpy,
 		int		nglyphs)
 {
     XftFontInt	    *font = (XftFontInt *) pub;
-    int		    i;
+    int		    i, j;
     FT_UInt	    missing[XFT_NMISSING];
     int		    nmissing;
     FT_UInt	    g, max;
     int		    size, width;
+    int		    dstx, dsty;
     Glyph	    wire;
+    XftGlyph*       glyph;
     char	    *char8;
     unsigned short  *char16;
     unsigned int    *char32;
@@ -141,22 +143,46 @@ XftGlyphRender (Display		*dpy,
 	if (!chars)
 	    goto bail1;
     }
+    dstx = x;
+    dsty = y;
     char8 = (char *) chars;
     char16 = (unsigned short *) chars;
     char32 = (unsigned int *) chars;
-    for (i = 0; i < nglyphs; i++)
+    for (i = 0, j = 0; i < nglyphs; i++)
     {
 	wire = (Glyph) glyphs[i];
 	if (wire >= (Glyph) font->num_glyphs || !font->glyphs[wire])
 	    wire = 0;
-	switch (width) {
-	case 1: char8[i] = (char) wire; break;
-	case 2: char16[i] = (unsigned short) wire; break;
-	case 4: char32[i] = (unsigned int) wire; break;
+        glyph = font->glyphs[wire];
+	if (glyph->picture)
+	{
+	    _XftCompositeString(dpy, op, src, dst, font->format, font->glyphset,
+	                        srcx, srcy, x, y, width, chars, j);
+	    XRenderComposite(dpy, PictOpOver, glyph->picture, None,
+	                     dst, 0, 0, 0, 0, dstx, dsty - glyph->metrics.y,
+	                     glyph->metrics.width, glyph->metrics.height);
+
+	    dstx += glyph->metrics.xOff;
+	    dsty += glyph->metrics.yOff;
+
+	    x = dstx;
+	    y = dsty;
+	    j = 0;
+	}
+	else
+	{
+	    switch (width) {
+	    case 1: char8[j] = (char) wire; break;
+	    case 2: char16[j] = (unsigned short) wire; break;
+	    case 4: char32[j] = (unsigned int) wire; break;
+	    }
+	    dstx += glyph->metrics.xOff;
+	    dsty += glyph->metrics.yOff;
+	    ++j;
 	}
     }
     _XftCompositeString(dpy, op, src, dst, font->format, font->glyphset,
-                        srcx, srcy, x, y, width, chars, nglyphs);
+                        srcx, srcy, x, y, width, chars, j);
     if (chars != char_local)
 	free (chars);
 bail1:
@@ -319,9 +345,10 @@ XftGlyphSpecRender (Display		    *dpy,
 	    g = 0;
 	/*
 	 * check to see if the glyph is placed where it would
-	 * fall using the normal spacing
+	 * fall using the normal spacing and if it would render
+	 * as a XRender glyph
 	 */
-	if ((glyph = font->glyphs[g]))
+	if ((glyph = font->glyphs[g]) && !glyph->picture)
 	{
 	    if (x != glyphs[i].x || y != glyphs[i].y)
 	    {
@@ -335,7 +362,7 @@ XftGlyphSpecRender (Display		    *dpy,
     }
 
     elts = elts_local;
-    if (nelt > NUM_ELT_LOCAL)
+    if (!font->info.color && nelt > NUM_ELT_LOCAL)
     {
 	elts = AllocGlyphElt8Array (nelt);
 	if (!elts)
@@ -343,7 +370,7 @@ XftGlyphSpecRender (Display		    *dpy,
     }
 
     /*
-     * Generate the list of glyph elts
+     * Generate the list of glyph elts or render color glyphs
      */
     nelt = 0;
     x = y = 0;
@@ -357,6 +384,14 @@ XftGlyphSpecRender (Display		    *dpy,
 	    g = 0;
 	if ((glyph = font->glyphs[g]))
 	{
+	    if (glyph->picture)
+	    {
+                XRenderComposite(dpy, PictOpOver, glyph->picture, None,
+                                 dst, 0, 0, 0, 0,
+                                 glyphs[i].x, glyphs[i].y - glyph->metrics.y,
+                                 glyph->metrics.width, glyph->metrics.height);
+                continue;
+	    }
 	    if (!i || x != glyphs[i].x || y != glyphs[i].y)
 	    {
 		if (n)
@@ -592,7 +627,7 @@ XftGlyphFontSpecRender (Display			    *dpy,
 	 * check to see if the glyph is placed where it would
 	 * fall using the normal spacing
 	 */
-	if ((glyph = font->glyphs[g]))
+	if ((glyph = font->glyphs[g]) && !glyph->picture)
 	{
 	    if (pub != prevPublic || x != glyphs[i].x || y != glyphs[i].y)
 	    {
@@ -617,7 +652,7 @@ XftGlyphFontSpecRender (Display			    *dpy,
     }
 
     /*
-     * Generate the list of glyph elts
+     * Generate the list of glyph elts and render color glyphs
      */
     nelt = 0;
     x = y = 0;
@@ -635,6 +670,14 @@ XftGlyphFontSpecRender (Display			    *dpy,
 	    g = 0;
 	if ((glyph = font->glyphs[g]))
 	{
+	    if (glyph->picture)
+	    {
+                XRenderComposite(dpy, PictOpOver, glyph->picture, None,
+                                 dst, 0, 0, 0, 0,
+                                 glyphs[i].x, glyphs[i].y - glyph->metrics.y,
+                                 glyph->metrics.width, glyph->metrics.height);
+                continue;
+	    }
 	    if (!i || pub != prevPublic || x != glyphs[i].x || y != glyphs[i].y)
 	    {
 		if (n)