More notes on glyphsglyph

1 files changed, 114 insertions, 0 deletions

diff --git a/glyphs.txt b/glyphs.txt
index 95e6958e..564566e8 100644
--- a/glyphs.txt
+++ b/glyphs.txt
@@ -1,3 +1,117 @@
+New approach:
+
+Pixman has the concept of a glyph cache, and not the concept of a
+glyph set.
+
+API:
+
+pixman_glyph_cache_freeze();
+pixman_glyph_cache_thaw();
+bool pixman_glyph_cache_contains(cache, void *font, uint32_t index);
+void pixman_glyph_cache_insert(cache, void *font, uint32_t index, 
+     format, x, y, data, ...);
+struct command
+{
+	union
+	{
+		struct
+		{
+		    void *font;
+		} switch;
+
+		struct
+		{
+		    int x, y;
+		} displace;
+
+		struct
+		{
+		    uint32_t n_glyphs;
+		} glyphs;
+	} u;
+};
+
+pixman_glyph_commands_t *pixman_glyph_commands_begin (void *data, int n_bytes);
+
+pixman_glyph_commands_t *pixman_glyph_commands_switch (void *data, void *font);
+... *pixman_glyph_commands_displace (void *data, int x, int y);
+... *pixman_glyph_commands_glyphs (void *data, uint32_t n_glyphs,
+     				    uint32_t *indices);
+
+void *pixman_glyph_commands_end (void *data);
+void  pixman_glyph_commands_free (void *data);
+
+
+void pixman_composite_glyphs(..., src, cache, commands, dst);
+
+To use it, you would do:
+
+	uint8_t data[1024];
+	uint32_t glyphs[N_STACK_GLYPHS];
+	uint32_t *g = glyphs;
+
+	pixman_glyph_commands_t *commands;
+
+	pixman_glyph_cache_freeze();
+
+	commands = pixman_glyph_commands_begin (data, sizeof (data));	
+
+	for (i = 0; i < blah; ++i)
+	{
+		if (glyph)
+		{
+		    if (g - glyphs == N_STACK_GLYPHS)
+		    {
+			command = add_glyphs (command, font, glyphs, N_STACK_GLYPHS);
+			g = glyphs;
+		     }
+		     *g++ = index;
+		}
+		else
+		{
+		     command = add_glyphs (command, font, glyphs, g - glyphs);
+		     g = glyphs;
+
+		     if (displace)
+		     	...;
+		     else if (font)
+		     	...;
+		}
+	}
+
+	command = add_glyphs (command, font, glyphs, g - glyphs);
+	commands = pixman_glyph_commands_end (commands);
+
+	pixman_composite_glyphs (src, cache, commands, dst, ...);
+
+	pixman_glyph_commands_free (commands);
+
+
+In the X server, do we get any notification when a glyph disappears?
+Yes, we do in UnrealizeGlyph().
+
+We can be even simpler than this:
+
+pixman_glyph_cache_freeze();
+pixman_glyph_cache_thaw();
+bool pixman_glyph_cache_contains(cache, void *font, void *index);
+void pixman_glyph_cache_insert(cache, void *font, void *index, 
+     format, x, y, data, ...);
+pixman_composite_glyphs (src, 
+			 void *font, void **indices, int n_indices, 
+			 pixman_format_t mask_format,
+			 dst, 
+			 ...);
+
+where the X server void use NULL for font, and the glyph pointer for
+indices, and cairo would use scaled_font for font and the
+glyph_indices for the indices.
+
+mask_format would determine the format used for the mask, although
+another possibility would be to say that a8 glyphs are expanded to
+shades of white. Or saying that glyphs get added with a white source.
+
+
 Glyphs in the X server
 
 - Glyphsets are current global and not attached to a screen and