all: Add SIXEL support

This adds support for SIXEL images to VTE. Based on initial work by
Hayaki Saito <saitoha@me.com>, updated and improved by
Hans Petter Jansson <hpj@cl.no>

For now this is off by default; build with -Dsixel=true to enable.

(This is the contents of the wip/sixels branch, squashed together
into one commit.)

https://gitlab.gnome.org/GNOME/vte/-/issues/253

1 files changed, 102 insertions, 0 deletions

diff --git a/src/image.hh b/src/image.hh
new file mode 100644
index 00000000..fa972c9b
--- /dev/null
+++ b/src/image.hh
@@ -0,0 +1,102 @@
+/*
+ * Copyright © 2016-2020 Hayaki Saito <saitoha@me.com>
+ * Copyright © 2020 Hans Petter Jansson <hpj@cl.no>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <pango/pangocairo.h>
+#include "cairo-glue.hh"
+
+namespace vte {
+
+namespace image {
+
+class Image {
+private:
+        // Device-friendly Cairo surface
+        vte::cairo::Surface m_surface{};
+
+        // Draw/prune priority, must be unique
+        int m_priority;
+
+        // Image dimensions in pixels
+        int m_width_pixels;
+        int m_height_pixels;
+
+        // Top left corner offset in cell units
+        int m_left_cells;
+        int m_top_cells;
+
+        // Cell dimensions in pixels at time of image creation
+        int m_cell_width;
+        int m_cell_height;
+
+public:
+        Image(vte::cairo::Surface&& surface,
+              int priority,
+              int width_pixels,
+              int height_pixels,
+              int col,
+              int row,
+              int cell_width,
+              int cell_height) noexcept
+                : m_surface{std::move(surface)},
+                  m_priority{priority},
+                  m_width_pixels{width_pixels},
+                  m_height_pixels{height_pixels},
+                  m_left_cells{col},
+                  m_top_cells{row},
+                  m_cell_width{cell_width},
+                  m_cell_height{cell_height}
+        {
+        }
+
+        ~Image() = default;
+
+        Image(Image const&) = delete;
+        Image(Image&&) = delete;
+        Image operator=(Image const&) = delete;
+        Image operator=(Image&&) = delete;
+
+        inline constexpr auto get_priority() const noexcept { return m_priority; }
+        inline constexpr auto get_left() const noexcept { return m_left_cells; }
+        inline auto get_top() const noexcept { return m_top_cells; }
+        inline void set_top(int row) noexcept { m_top_cells = row; }
+        inline constexpr auto get_width() const noexcept { return (m_width_pixels + m_cell_width - 1) / m_cell_width; }
+        inline constexpr auto get_height() const noexcept { return (m_height_pixels + m_cell_height - 1) / m_cell_height; }
+        inline auto get_bottom() const noexcept { return m_top_cells + get_height() - 1; }
+
+        inline auto resource_size() const noexcept
+        {
+                if (cairo_image_surface_get_stride(m_surface.get()) != 0)
+                        return cairo_image_surface_get_stride(m_surface.get()) * m_height_pixels;
+
+                /* Not an image surface: Only the device knows for sure, so we guess */
+                return m_width_pixels * m_height_pixels * 4;
+        }
+
+        void paint(cairo_t* cr,
+                   int offset_x,
+                   int offset_y,
+                   int cell_width,
+                   int cell_height) const noexcept;
+
+}; // class Image
+
+} // namespace image
+
+} // namespace vte