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Make FreeType select a size for fixed sized fonts

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and scale it down before adding it to atlas to save on atlas space.
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Green Sky 2025-10-22 21:52:07 +02:00
parent b46f099a3f
commit f8e941e72f
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1 changed files with 103 additions and 22 deletions
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125
misc/freetype/imgui_freetype.cpp
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@ -108,7 +108,7 @@ static FT_Error ImGuiLunasvgPortPresetSlot(FT_GlyphSlot slot, FT_Bool cache, FT_
//-------------------------------------------------------------------------
#define FT_CEIL(X) (((X + 63) & -64) / 64) // From SDL_ttf: Handy routines for converting from fixed point
#define FT_SCALEFACTOR 64.0f
#define FT_SCALEFACTOR 64.0f // For converting from/to 26.6 factionals
// Glyph metrics:
// --------------
@ -435,19 +435,58 @@ static bool ImGui_ImplFreeType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig* s
FT_New_Size(bd_font_data->FtFace, &bd_baked_data->FtSize);
FT_Activate_Size(bd_baked_data->FtSize);
// Vuhdo 2017: "I'm not sure how to deal with font sizes properly. As far as I understand, currently ImGui assumes that the 'pixel_height'
// is a maximum height of an any given glyph, i.e. it's the sum of font's ascender and descender. Seems strange to me.
// FT_Set_Pixel_Sizes() doesn't seem to get us the same result."
// (FT_Set_Pixel_Sizes() essentially calls FT_Request_Size() with FT_SIZE_REQUEST_TYPE_NOMINAL)
const float rasterizer_density = src->RasterizerDensity * baked->RasterizerDensity;
FT_Size_RequestRec req;
req.type = (bd_font_data->UserFlags & ImGuiFreeTypeLoaderFlags_Bitmap) ? FT_SIZE_REQUEST_TYPE_NOMINAL : FT_SIZE_REQUEST_TYPE_REAL_DIM;
req.width = 0;
req.height = (uint32_t)(size * 64 * rasterizer_density);
req.horiResolution = 0;
req.vertResolution = 0;
FT_Request_Size(bd_font_data->FtFace, &req);
if (((bd_font_data->FtFace->face_flags & FT_FACE_FLAG_FIXED_SIZES) != 0) && ((bd_font_data->FtFace->face_flags & FT_FACE_FLAG_SCALABLE) == 0) && ((bd_font_data->UserFlags & ImGuiFreeTypeLoaderFlags_Bitmap) != 0))
{
IM_ASSERT(bd_font_data->FtFace->num_fixed_sizes > 0);
// Loop over sizes and pick the closest, larger (or better equal) size.
int best_index = 0;
float best_height = bd_font_data->FtFace->available_sizes[best_index].y_ppem / FT_SCALEFACTOR;
for (int i = 1; i < bd_font_data->FtFace->num_fixed_sizes; i++)
{
const float cur_height = bd_font_data->FtFace->available_sizes[i].y_ppem / FT_SCALEFACTOR;
// TODO: is this overkill?
// TODO: is-float-close with epsilon param would be nice, maybe
if (ImFabs(cur_height - size) < 0.001f)
{
best_index = i;
break;
}
else if (cur_height < size)
{
if (best_height < cur_height)
{
best_index = i;
best_height = cur_height;
}
}
else
{
if (best_height > cur_height)
{
best_index = i;
best_height = cur_height;
}
}
}
FT_Select_Size(bd_font_data->FtFace, best_index);
}
else
{
// Vuhdo 2017: "I'm not sure how to deal with font sizes properly. As far as I understand, currently ImGui assumes that the 'pixel_height'
// is a maximum height of an any given glyph, i.e. it's the sum of font's ascender and descender. Seems strange to me.
// FT_Set_Pixel_Sizes() doesn't seem to get us the same result."
// (FT_Set_Pixel_Sizes() essentially calls FT_Request_Size() with FT_SIZE_REQUEST_TYPE_NOMINAL)
FT_Size_RequestRec req;
req.type = (bd_font_data->UserFlags & ImGuiFreeTypeLoaderFlags_Bitmap) ? FT_SIZE_REQUEST_TYPE_NOMINAL : FT_SIZE_REQUEST_TYPE_REAL_DIM;
req.width = 0;
req.height = (uint32_t)(size * FT_SCALEFACTOR * rasterizer_density);
req.horiResolution = 0;
req.vertResolution = 0;
FT_Request_Size(bd_font_data->FtFace, &req);
}
// Output
if (src->MergeMode == false)
@ -497,9 +536,21 @@ static bool ImGui_ImplFreeType_FontBakedLoadGlyph(ImFontAtlas* atlas, ImFontConf
FT_Face face = bd_font_data->FtFace;
FT_GlyphSlot slot = face->glyph;
const float rasterizer_density = src->RasterizerDensity * baked->RasterizerDensity;
float bitmap_x_scale = 1.f;
float bitmap_y_scale = 1.f;
if (((face->face_flags & FT_FACE_FLAG_FIXED_SIZES) != 0) && ((face->face_flags & FT_FACE_FLAG_SCALABLE) == 0) && ((bd_font_data->UserFlags & ImGuiFreeTypeLoaderFlags_Bitmap) != 0))
{
// TODO: what if this just means invisible?
IM_ASSERT(bd_font_data->FtFace->size->metrics.x_ppem > 0);
IM_ASSERT(bd_font_data->FtFace->size->metrics.y_ppem > 0);
// Scale fixed size bitmap to target size
bitmap_x_scale = baked->Size / bd_font_data->FtFace->size->metrics.x_ppem;
bitmap_y_scale = baked->Size / bd_font_data->FtFace->size->metrics.y_ppem;
}
// Load metrics only mode
const float advance_x = (slot->advance.x / FT_SCALEFACTOR) / rasterizer_density;
const float advance_x = ((slot->advance.x / FT_SCALEFACTOR) * bitmap_x_scale) / rasterizer_density;
if (out_advance_x != NULL)
{
IM_ASSERT(out_glyph == NULL);
@ -514,9 +565,9 @@ static bool ImGui_ImplFreeType_FontBakedLoadGlyph(ImFontAtlas* atlas, ImFontConf
if (error != 0 || ft_bitmap == nullptr)
return false;
const int w = (int)ft_bitmap->width;
const int h = (int)ft_bitmap->rows;
const bool is_visible = (w != 0 && h != 0);
const int bitmap_w = (int)ft_bitmap->width;
const int bitmap_h = (int)ft_bitmap->rows;
const bool is_visible = (bitmap_w != 0 && bitmap_h != 0);
// Prepare glyph
out_glyph->Codepoint = codepoint;
@ -525,6 +576,11 @@ static bool ImGui_ImplFreeType_FontBakedLoadGlyph(ImFontAtlas* atlas, ImFontConf
// Pack and retrieve position inside texture atlas
if (is_visible)
{
const int w = (int)ImFloor(bitmap_w * bitmap_x_scale);
const int h = (int)ImFloor(bitmap_h * bitmap_y_scale);
IM_ASSERT(!((h < bitmap_h && w > bitmap_w) || (h > bitmap_h && w < bitmap_w))); // Can't up AND downscale at the same time // TODO: or can we?
const bool down_scaling = h < bitmap_h || w < bitmap_w;
ImFontAtlasRectId pack_id = ImFontAtlasPackAddRect(atlas, w, h);
if (pack_id == ImFontAtlasRectId_Invalid)
{
@ -534,10 +590,35 @@ static bool ImGui_ImplFreeType_FontBakedLoadGlyph(ImFontAtlas* atlas, ImFontConf
}
ImTextureRect* r = ImFontAtlasPackGetRect(atlas, pack_id);
// Render pixels to our temporary buffer
atlas->Builder->TempBuffer.resize(w * h * 4);
// Render pixels to our temporary buffer, while making sure we have space for an extra copy used during downscaling.
atlas->Builder->TempBuffer.resize(((down_scaling ? bitmap_w * bitmap_h : 0) + w * h) * 4);
uint32_t* temp_buffer = (uint32_t*)atlas->Builder->TempBuffer.Data;
ImGui_ImplFreeType_BlitGlyph(ft_bitmap, temp_buffer, w);
// Blit (and convert) into the first bm_w * bm_h * 4 bytes.
ImGui_ImplFreeType_BlitGlyph(ft_bitmap, temp_buffer, bitmap_w);
if (down_scaling)
{
uint32_t* dst_buffer = temp_buffer + bitmap_w * bitmap_h;
// Perform downscale, from temp_buffer (bitmap_w * bitmap_h) to dst_buffer (w * h)
#if 1
// Point Sampling / Nearest Neighbor
for (int y = 0; y < h; y++)
{
const int bitmap_y = ImFloor(((y + 0.5f) * bitmap_h) / h);
for (int x = 0; x < w; x++)
{
const int bitmap_x = ImFloor(((x + 0.5f) * bitmap_w) / w);
dst_buffer[y * w + x] = temp_buffer[bitmap_y * bitmap_w + bitmap_x];
}
}
#else
// TODO: box scaling
#endif
// Redirect to downscaled part of the buffer
temp_buffer = dst_buffer;
}
const float ref_size = baked->ContainerFont->Sources[0]->SizePixels;
const float offsets_scale = (ref_size != 0.0f) ? (baked->Size / ref_size) : 1.0f;
@ -551,8 +632,8 @@ static bool ImGui_ImplFreeType_FontBakedLoadGlyph(ImFontAtlas* atlas, ImFontConf
float recip_v = 1.0f / rasterizer_density;
// Register glyph
float glyph_off_x = (float)face->glyph->bitmap_left;
float glyph_off_y = (float)-face->glyph->bitmap_top;
float glyph_off_x = ImFloor((float)face->glyph->bitmap_left * bitmap_x_scale);
float glyph_off_y = ImFloor((float)-face->glyph->bitmap_top * bitmap_y_scale);
out_glyph->X0 = glyph_off_x * recip_h + font_off_x;
out_glyph->Y0 = glyph_off_y * recip_v + font_off_y;
out_glyph->X1 = (glyph_off_x + w) * recip_h + font_off_x;