From b7ec13af49bd3ce6a576062ec0ee1c5d0add2cfc Mon Sep 17 00:00:00 2001
From: Pascal Thomet <pthomet@gmail.com>
Date: Thu, 8 Aug 2024 12:21:01 +0200
Subject: [PATCH] Added support to render OpenType SVG fonts using plutosvg as
 an alternative to lunasvg (fix #7187)

<SVG Fonts include a set of SVG documents. As per the [OpenType specification](https://learn.microsoft.com/en-us/typography/opentype/spec/svg#glyph-identifiers),
some SVG fonts (such as NotoColorEmoji) may group several glyphs in a common svg document (by selecting a subset of the elements in this document).

LunaSvg does support fonts where each glyph is associated to a distinct document. Unfortunately, it is not able to render
a subset of a svg document, and will likely not be able to do so in the future.

Its cousin project plutosvg (by the same author), is able to do it, and provides ready to use freetype hooks.

Example: https://github.com/sammycage/lunasvg/issues/150 shows an example where a single svg document
included in the font may contains thousands of glyphs (each glyph is a subset of the svg document).

Pros and Cons
-------------
Since this commit adds some complexity in the code here is a study of the pros and cons:

Pros:
- plutosvg is faster than lunasvg
- freetype hooks are provided by plutosvg (no need to provide them in imgui_freetype.cpp)

Cons:
- the compilation setup for plutosvg is a bit more complex than for lunasvg (requires plutovg + plutosvg)
- no offical release is available yet for plutosvg. No vcpkg package available yet.
- having two competing compilation flags is not ideal (IMGUI_ENABLE_FREETYPE_LUNASVG vs IMGUI_ENABLE_FREETYPE_PLUTOSVG)
  (it may be possible to remove IMGUI_ENABLE_FREETYPE_LUNASVG in the future, at the cost of breaking some users build upon upgrade)

Compilation hints for plutovg/plutosvg
--------------------------------------
_Compilation hints for plutovg_
- Compile all source files in `plutovg/source/*.c`
- Add include directory: `plutovg/include` + `plutovg/stb`

_Compilation hints for plutosvg_
- Compile `plutosvg/source/plutosvg.c`
- Add include directory: `plutosvg/source`
- Add define: `PLUTOSVG_HAS_FREETYPE`
- Link with: plutovg, freetype

Demonstration repository
-------------------------
https://github.com/pthom/lunasvg_perf_issue
---
 docs/CHANGELOG.txt               |  4 +++-
 imconfig.h                       |  9 ++++++---
 misc/freetype/README.md          | 20 +++++++++++++++++++-
 misc/freetype/imgui_freetype.cpp | 22 ++++++++++++++++++----
 4 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt
index d19e8f39e063..13cf1c098ddd 100644
--- a/docs/CHANGELOG.txt
+++ b/docs/CHANGELOG.txt
@@ -66,7 +66,9 @@ Breaking changes:
    - new ImageButton() always use style.FramePadding, which you can freely override with PushStyleVar()/PopStyleVar().
 
 Other changes:
-
+- Fonts, imgui_freetype: Added support to render OpenType SVG fonts using plutosvg as an alternative to lunasvg
+  Requires enabling IMGUI_ENABLE_FREETYPE_PLUTOSVG along with IMGUI_ENABLE_FREETYPE,
+  and providing headers/libraries for plutosvg + plutovg
 - IO: Added GetPlatformIO() and ImGuiPlatformIO, pulled from 'docking' branch, which
   is a centralized spot to connect os/platform/renderer related functions.
   Clipboard, IME and OpenInShell hooks are moved here. (#7660)
diff --git a/imconfig.h b/imconfig.h
index b8d55842b9bf..02346aa0b394 100644
--- a/imconfig.h
+++ b/imconfig.h
@@ -83,10 +83,13 @@
 // On Windows you may use vcpkg with 'vcpkg install freetype --triplet=x64-windows' + 'vcpkg integrate install'.
 //#define IMGUI_ENABLE_FREETYPE
 
-//---- Use FreeType+lunasvg library to render OpenType SVG fonts (SVGinOT)
-// Requires lunasvg headers to be available in the include path + program to be linked with the lunasvg library (not provided).
+//---- render OpenType SVG fonts (SVGinOT) via plutosvg or lunasvg
+// Two alternatives are possible to render SVG fonts: either use lunasvg (added 2023/11), or use plutosvg (added in 2024)
+// (plutosvg will support more fonts and may load them faster)
+// Both alternatives require the headers to be available in the include path + program to be linked with the lunasvg or plutosvg library (not provided).
 // Only works in combination with IMGUI_ENABLE_FREETYPE.
-// (implementation is based on Freetype's rsvg-port.c which is licensed under CeCILL-C Free Software License Agreement)
+// (lunasvg implementation is based on Freetype's rsvg-port.c which is licensed under CeCILL-C Free Software License Agreement)
+//#define IMGUI_ENABLE_FREETYPE_PLUTOSVG
 //#define IMGUI_ENABLE_FREETYPE_LUNASVG
 
 //---- Use stb_truetype to build and rasterize the font atlas (default)
diff --git a/misc/freetype/README.md b/misc/freetype/README.md
index 275a5386641d..0c3b493f2665 100644
--- a/misc/freetype/README.md
+++ b/misc/freetype/README.md
@@ -38,7 +38,25 @@ You can use the `ImGuiFreeTypeBuilderFlags_LoadColor` flag to load certain color
 
 ### Using OpenType SVG fonts (SVGinOT)
 - *SVG in Open Type* is a standard by Adobe and Mozilla for color OpenType and Open Font Format fonts. It allows font creators to embed complete SVG files within a font enabling full color and even animations.
-- Popular fonts such as [twemoji](https://github.com/13rac1/twemoji-color-font) and fonts made with [scfbuild](https://github.com/13rac1/scfbuild) is SVGinOT
+- Popular fonts such as [twemoji](https://github.com/13rac1/twemoji-color-font) and fonts made with [scfbuild](https://github.com/13rac1/scfbuild) is SVGinOT 
+- Two alternatives are possible to render SVG fonts: either use lunasvg (support added in november 2023), or use "plutosvg" (support added late 2024). plutosvg will support some more fonts (for example NotoColorEmoji-Regular) and may load them faster.
+
+#### Using lunasvg
 - Requires: [lunasvg](https://github.com/sammycage/lunasvg) v2.3.2 and above
     1. Add `#define IMGUI_ENABLE_FREETYPE_LUNASVG` in your `imconfig.h`.
     2. Get latest lunasvg binaries or build yourself. Under Windows you may use vcpkg with: `vcpkg install lunasvg --triplet=x64-windows`.
+
+#### Using plutosvg (and plutovg)
+1. Add `#define IMGUI_ENABLE_FREETYPE_PLUTOSVG` in your `imconfig.h`.
+2. Compile and link with plutosvg *and* plutovg (which is required by plutosvg)
+
+_Compilation hints for plutovg_
+- Compile all source files in `plutovg/source/*.c`
+- Add include directory: `plutovg/include` + `plutovg/stb`
+
+_Compilation hints for plutosvg_
+- Compile `plutosvg/source/plutosvg.c`
+- Add include directory: `plutosvg/source`
+- Add define: `PLUTOSVG_HAS_FREETYPE`
+- Link with: plutovg, freetype
+
diff --git a/misc/freetype/imgui_freetype.cpp b/misc/freetype/imgui_freetype.cpp
index d97605b25868..84c677b483d3 100644
--- a/misc/freetype/imgui_freetype.cpp
+++ b/misc/freetype/imgui_freetype.cpp
@@ -6,6 +6,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2024/08/27: improved support for SVG Fonts, by providing IMGUI_ENABLE_FREETYPE_PLUTOSVG, as an alternative to IMGUI_ENABLE_FREETYPE_LUNASVG
 //  2023/11/13: added support for ImFontConfig::RasterizationDensity field for scaling render density without scaling metrics.
 //  2023/08/01: added support for SVG fonts, enable by using '#define IMGUI_ENABLE_FREETYPE_LUNASVG' (#6591)
 //  2023/01/04: fixed a packing issue which in some occurrences would prevent large amount of glyphs from being packed correctly.
@@ -45,12 +46,21 @@
 #include FT_GLYPH_H             // <freetype/ftglyph.h>
 #include FT_SYNTHESIS_H         // <freetype/ftsynth.h>
 
-#ifdef IMGUI_ENABLE_FREETYPE_LUNASVG
+// Handle LunaSVG and PlutoSVG
+#if defined(IMGUI_ENABLE_FREETYPE_LUNASVG) && defined(IMGUI_ENABLE_FREETYPE_PLUTOSVG)
+#error "Cannot enable both IMGUI_ENABLE_FREETYPE_LUNASVG and IMGUI_ENABLE_FREETYPE_PLUTOSVG"
+#endif
+#ifdef  IMGUI_ENABLE_FREETYPE_LUNASVG
 #include FT_OTSVG_H             // <freetype/otsvg.h>
 #include FT_BBOX_H              // <freetype/ftbbox.h>
 #include <lunasvg.h>
+#endif
+#ifdef  IMGUI_ENABLE_FREETYPE_PLUTOSVG
+#include <plutosvg.h>
+#endif
+#if defined(IMGUI_ENABLE_FREETYPE_LUNASVG) || defined (IMGUI_ENABLE_FREETYPE_PLUTOSVG)
 #if !((FREETYPE_MAJOR >= 2) && (FREETYPE_MINOR >= 12))
-#error IMGUI_ENABLE_FREETYPE_LUNASVG requires FreeType version >= 2.12
+#error IMGUI_ENABLE_FREETYPE_PLUTOSVG or IMGUI_ENABLE_FREETYPE_LUNASVG requires FreeType version >= 2.12
 #endif
 #endif
 
@@ -269,11 +279,11 @@ namespace
 
         // Need an outline for this to work
         FT_GlyphSlot slot = Face->glyph;
-#ifdef IMGUI_ENABLE_FREETYPE_LUNASVG
+#if defined(IMGUI_ENABLE_FREETYPE_LUNASVG) || defined(IMGUI_ENABLE_FREETYPE_PLUTOSVG)
         IM_ASSERT(slot->format == FT_GLYPH_FORMAT_OUTLINE || slot->format == FT_GLYPH_FORMAT_BITMAP || slot->format == FT_GLYPH_FORMAT_SVG);
 #else
 #if ((FREETYPE_MAJOR >= 2) && (FREETYPE_MINOR >= 12))
-        IM_ASSERT(slot->format != FT_GLYPH_FORMAT_SVG && "The font contains SVG glyphs, you'll need to enable IMGUI_ENABLE_FREETYPE_LUNASVG in imconfig.h and install required libraries in order to use this font");
+        IM_ASSERT(slot->format != FT_GLYPH_FORMAT_SVG && "The font contains SVG glyphs, you'll need to enable IMGUI_ENABLE_FREETYPE_PLUTOSVG or IMGUI_ENABLE_FREETYPE_LUNASVG in imconfig.h and install required libraries in order to use this font");
 #endif
         IM_ASSERT(slot->format == FT_GLYPH_FORMAT_OUTLINE || slot->format == FT_GLYPH_FORMAT_BITMAP);
 #endif // IMGUI_ENABLE_FREETYPE_LUNASVG
@@ -810,6 +820,10 @@ static bool ImFontAtlasBuildWithFreeType(ImFontAtlas* atlas)
     SVG_RendererHooks hooks = { ImGuiLunasvgPortInit, ImGuiLunasvgPortFree, ImGuiLunasvgPortRender, ImGuiLunasvgPortPresetSlot };
     FT_Property_Set(ft_library, "ot-svg", "svg-hooks", &hooks);
 #endif // IMGUI_ENABLE_FREETYPE_LUNASVG
+#ifdef IMGUI_ENABLE_FREETYPE_PLUTOSVG
+    // With plutosvg, use provided hooks
+    FT_Property_Set(ft_library, "ot-svg", "svg-hooks", plutosvg_ft_svg_hooks());
+#endif // IMGUI_ENABLE_FREETYPE_PLUTOSVG
 
     bool ret = ImFontAtlasBuildWithFreeTypeEx(ft_library, atlas, atlas->FontBuilderFlags);
     FT_Done_Library(ft_library);