make font size be the em square's size when ImFontCfg::SizePixels is <= 0.0f

Author: cfillion

imgui_draw.cpp

@@ -4573,7 +4573,7 @@ static bool ImGui_ImplStbTrueType_FontSrcInit(ImFontAtlas* atlas, ImFontConfig*
     if (src->MergeMode && src->SizePixels == 0.0f)
         src->SizePixels = ref_size;
 
-    if (src->SizePixels >= 0.0f)
+    if (src->SizePixels > 0.0f)
         bd_font_data->ScaleFactor = stbtt_ScaleForPixelHeight(&bd_font_data->FontInfo, 1.0f);
     else
         bd_font_data->ScaleFactor = stbtt_ScaleForMappingEmToPixels(&bd_font_data->FontInfo, 1.0f);
@@ -4610,13 +4610,12 @@ static bool ImGui_ImplStbTrueType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig
     if (src->MergeMode == false)
     {
         // FIXME-NEWFONTS: reevaluate how to use sizing metrics
-        // FIXME-NEWFONTS: make use of line gap value
         float scale_for_layout = bd_font_data->ScaleFactor * baked->Size;
         int unscaled_ascent, unscaled_descent, unscaled_line_gap;
         stbtt_GetFontVMetrics(&bd_font_data->FontInfo, &unscaled_ascent, &unscaled_descent, &unscaled_line_gap);
         baked->Ascent = ImCeil(unscaled_ascent * scale_for_layout);
         baked->Descent = ImFloor(unscaled_descent * scale_for_layout);
-        baked->LineHeight = baked->Size;
+        baked->LineHeight = src->SizePixels > 0.0f ? baked->Size : baked->Ascent - baked->Descent + ImFloor(unscaled_line_gap * scale_for_layout);
     }
     return true;
 }

misc/freetype/imgui_freetype.cpp

@@ -442,7 +442,7 @@ bool ImGui_ImplFreeType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig* src, ImF
     // (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.type = src->SizePixels <= 0.0f ? 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;
@@ -455,10 +455,10 @@ bool ImGui_ImplFreeType_FontBakedInit(ImFontAtlas* atlas, ImFontConfig* src, ImF
         // Read metrics
         FT_Size_Metrics metrics = bd_baked_data->FtSize->metrics;
         const float scale = 1.0f / rasterizer_density;
-        baked->Ascent     = (float)FT_CEIL(metrics.ascender)  * scale;      // The pixel extents above the baseline in pixels (typically positive).
-        baked->Descent    = (float)FT_CEIL(metrics.descender) * scale;      // The extents below the baseline in pixels (typically negative).
-        baked->LineHeight = baked->Size; // (float)FT_CEIL(metrics.height) * scale;      // The baseline-to-baseline distance. Note that it usually is larger than the sum of the ascender and descender taken as absolute values. There is also no guarantee that no glyphs extend above or below subsequent baselines when using this distance. Think of it as a value the designer of the font finds appropriate.
-        //LineGap         = (float)FT_CEIL(metrics.height - metrics.ascender + metrics.descender) * scale; // The spacing in pixels between one row's descent and the next row's ascent.
+        baked->Ascent     = (float)FT_CEIL(metrics.ascender) * scale;       // The pixel extents above the baseline in pixels (typically positive).
+        baked->Descent    = (float)(metrics.descender >> 6)  * scale;       // The extents below the baseline in pixels (typically negative).
+        // FreeType rounds metrics.height when GRID_FIT_METRICS is defined which may undesirably be 1px smaller than Ascent-Descent
+        baked->LineHeight = src->SizePixels > 0.0f ? baked->Size : (float)FT_CEIL(FT_MulFix(bd_font_data->FtFace->height, metrics.y_scale)) * scale; // The baseline-to-baseline distance. Note that it usually is larger than the sum of the ascender and descender taken as absolute values. There is also no guarantee that no glyphs extend above or below subsequent baselines when using this distance. Think of it as a value the designer of the font finds appropriate.
         //MaxAdvanceWidth = (float)FT_CEIL(metrics.max_advance) * scale;    // This field gives the maximum horizontal cursor advance for all glyphs in the font.
     }
     return true;