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ImFontAtlas: heuristic increase texture width up to 4096 with 4000+ glyphs. Various comments (#491)

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This commit is contained in:
ocornut 2016-01-20 10:30:28 +00:00
parent 3922988dea
commit e585204d82
3 changed files with 15 additions and 6 deletions
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11
extra_fonts/README.txt
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@ -2,6 +2,8 @@
The code in imgui.cpp embeds a copy of 'ProggyClean.ttf' that you can use without any external files.
Those are only provided as a convenience, you can load your own .TTF files.
Fonts are rasterized in a single texture at the time of calling either of io.Fonts.GetTexDataAsAlpha8()/GetTexDataAsRGBA32()/Build().
---------------------------------
LOADING INSTRUCTIONS
---------------------------------
@ -20,10 +22,17 @@
ImFontConfig config;
config.OversampleH = 3;
config.OversampleV = 3;
config.OversampleV = 1;
config.GlyphExtraSpacing.x = 1.0f;
io.Fonts->AddFontFromFileTTF("font.ttf", size_pixels, &config);
If you have very large number of glyphs or multiple fonts:
- Mind the fact that some graphics drivers have texture size limitation.
- Set io.Fonts.TexDesiredWidth to specify a texture width to minimize texture height (see comment in ImFontAtlas::Build function).
- You may reduce oversampling, e.g. config.OversampleH = 2 or 1.
- Reduce glyphs ranges, consider calculating them based on your source data if this is possible.
Combine two fonts into one:
// Load main font

5
imgui.cpp
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@ -359,6 +359,7 @@
Q: How can I load multiple fonts?
A: Use the font atlas to pack them into a single texture:
(Read extra_fonts/README.txt and the code in ImFontAtlas for more details.)
ImGuiIO& io = ImGui::GetIO();
ImFont* font0 = io.Fonts->AddFontDefault();
@ -371,7 +372,7 @@
// Options
ImFontConfig config;
config.OversampleH = 3;
config.OversampleV = 3;
config.OversampleV = 1;
config.GlyphExtraSpacing.x = 1.0f;
io.Fonts->LoadFromFileTTF("myfontfile.ttf", size_pixels, &config);
@ -383,8 +384,6 @@
io.Fonts->LoadFromFileTTF("fontawesome-webfont.ttf", 16.0f, &config, ranges);
io.Fonts->LoadFromFileTTF("myfontfile.ttf", size_pixels, NULL, &config, io.Fonts->GetGlyphRangesJapanese());
Read extra_fonts/README.txt or ImFontAtlas class for more details.
Q: How can I display and input non-Latin characters such as Chinese, Japanese, Korean, Cyrillic?
A: When loading a font, pass custom Unicode ranges to specify the glyphs to load. ImGui will support UTF-8 encoding across the board.
Character input depends on you passing the right character code to io.AddInputCharacter(). The example applications do that.

5
imgui_draw.cpp
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@ -1244,8 +1244,9 @@ bool ImFontAtlas::Build()
}
}
// Start packing
TexWidth = (TexDesiredWidth > 0) ? TexDesiredWidth : (total_glyph_count > 2000) ? 2048 : (total_glyph_count > 1000) ? 1024 : 512; // Width doesn't actually matters much but some API/GPU have texture size limitations, and increasing width can decrease height.
// Start packing. We need a known width for the skyline algorithm. Using a cheap heuristic here to decide of width. User can override TexDesiredWidth if they wish.
// After packing is done, width shouldn't matter much, but some API/GPU have texture size limitations and increasing width can decrease height.
TexWidth = (TexDesiredWidth > 0) ? TexDesiredWidth : (total_glyph_count > 4000) ? 4096 : (total_glyph_count > 2000) ? 2048 : (total_glyph_count > 1000) ? 1024 : 512;
TexHeight = 0;
const int max_tex_height = 1024*32;
stbtt_pack_context spc;