Overlay: Font - add merge_fonts property

Components/Overlay/include/OgreFont.h

@@ -28,6 +28,7 @@ THE SOFTWARE
 #define _Font_H__
 
 #include "OgreOverlayPrerequisites.h"
+#include "OgrePrerequisites.h"
 #include "OgreResource.h"
 #include "OgreCommon.h"
 #include "OgreSharedPtr.h"
@@ -44,6 +45,8 @@ namespace Ogre
     /** \addtogroup Overlays
     *  @{
     */
+    class Font;
+    typedef SharedPtr<Font> FontPtr;
 
     /// decode UTF8 encoded bytestream to uint32 codepoints
     _OgreOverlayExport std::vector<uint32> utftoc32(String str);
@@ -124,12 +127,17 @@ namespace Ogre
         /// Range of code points to generate glyphs for (truetype only)
         CodePointRangeList mCodePointRangeList;
 
+        std::vector<FontPtr> mMergeFonts;
+
         /// Internal method for loading from ttf
         void createTextureFromFont(void);
 
         void loadImpl() override;
         void unloadImpl() override;
         size_t calculateSize(void) const override { return 0; } // permanent resource is in the texture
+
+        friend class ImGuiOverlay;
+        DataStreamPtr _getTTFData();
     public:
 
         /** Constructor.
@@ -287,6 +295,16 @@ namespace Ogre
         {
             return mCodePointRangeList;
         }
+
+        /** Add a font to merge with this one.
+
+            This is useful when you want to use a font for most of the characters, but
+            fall back to another font for characters not present in the current font. e.g. icons.
+        */
+        void addMergeFont(const FontPtr& font) { mMergeFonts.push_back(font); }
+
+        const std::vector<FontPtr>& getMergeFontList() const { return mMergeFonts; }
+
         /** Gets the material generated for this font, as a weak reference. 
 
             This will only be valid after the Font has been loaded. 
@@ -343,8 +361,6 @@ namespace Ogre
         */
         void _setMaterial(const MaterialPtr& mat);
     };
-
-    typedef SharedPtr<Font> FontPtr;
     /** @} */
     /** @} */
 }

Components/Overlay/src/OgreFont.cpp

@@ -328,14 +328,15 @@ namespace Ogre
         mTexture->load();
     }
     //---------------------------------------------------------------------
+    DataStreamPtr Font::_getTTFData()
+    {
+        // Locate ttf file, load it pre-buffered into memory by wrapping
+        // the original DataStream in a MemoryDataStream
+        return ResourceGroupManager::getSingleton().openResource(mSource, mGroup, this);
+    }
     void Font::loadResource(Resource* res)
     {
-        // Locate ttf file, load it pre-buffered into memory by wrapping the
-        // original DataStream in a MemoryDataStream
-        DataStreamPtr dataStreamPtr =
-            ResourceGroupManager::getSingleton().openResource(
-                mSource, mGroup, this);
-        MemoryDataStream ttfchunk(dataStreamPtr);
+        MemoryDataStream ttfchunk = _getTTFData();
 
         // If codepoints not supplied, assume ASCII
         if (mCodePointRangeList.empty())

Components/Overlay/src/OgreImGuiOverlay.cpp

@@ -123,9 +123,7 @@ ImFont* ImGuiOverlay::addFont(const String& name, const String& group)
                     StringUtil::format("Font '%s' not found in group '%s'", name.c_str(), group.c_str()));
 
     OgreAssert(font->getType() == FT_TRUETYPE, "font must be of FT_TRUETYPE");
-    DataStreamPtr dataStreamPtr =
-        ResourceGroupManager::getSingleton().openResource(font->getSource(), font->getGroup());
-    MemoryDataStream ttfchunk(dataStreamPtr, false); // transfer ownership to imgui
+    MemoryDataStream ttfchunk(font->_getTTFData(), false); // transfer ownership to imgui
 
     // convert codepoint ranges for imgui
     CodePointRange cprange;
@@ -149,8 +147,33 @@ ImFont* ImGuiOverlay::addFont(const String& name, const String& group)
 
     ImFontConfig cfg;
     strncpy(cfg.Name, name.c_str(), IM_ARRAYSIZE(cfg.Name) - 1);
-    return io.Fonts->AddFontFromMemoryTTF(ttfchunk.getPtr(), ttfchunk.size(), font->getTrueTypeSize() * vpScale, &cfg,
-                                          cprangePtr);
+    auto* ret = io.Fonts->AddFontFromMemoryTTF(ttfchunk.getPtr(), ttfchunk.size(), font->getTrueTypeSize() * vpScale,
+                                               &cfg, cprangePtr);
+
+    cfg.MergeMode = true;
+
+    for(const auto& mergeFont : font->getMergeFontList())
+    {
+        MemoryDataStream mergeTtfchunk(mergeFont->_getTTFData(), false); // transfer ownership to imgui
+
+        CodePointRange mergeCprange;
+        for (const auto& r : mergeFont->getCodePointRangeList())
+        {
+            mergeCprange.push_back(r.first);
+            mergeCprange.push_back(r.second);
+        }
+
+        OgreAssert(!mergeCprange.empty(), "merge font must have codepoint ranges");
+        mergeCprange.push_back(0); // terminate
+        mCodePointRanges.push_back(mergeCprange);
+        cprangePtr = mCodePointRanges.back().data();
+
+        cfg.MergeMode = true;
+        ret = io.Fonts->AddFontFromMemoryTTF(mergeTtfchunk.getPtr(), mergeTtfchunk.size(),
+                                             mergeFont->getTrueTypeSize() * vpScale, &cfg, cprangePtr);
+    }
+
+    return ret;
 }
 
 void ImGuiOverlay::ImGUIRenderable::createFontTexture()

Components/Overlay/src/OgreOverlayTranslator.cpp

@@ -106,6 +106,31 @@ void FontTranslator::parseAttribute(ScriptCompiler* compiler, FontPtr& pFont,
         pFont->setAntialiasColour(flag);
         compiler->addError(ScriptCompiler::CE_DEPRECATEDSYMBOL, prop->file, prop->line, attrib);
     }
+    else if(attrib == "merge_fonts")
+    {
+        if (prop->values.empty())
+        {
+            compiler->addError(ScriptCompiler::CE_INVALIDPARAMETERS, prop->file, prop->line);
+            return;
+        }
+
+        for (auto& v : prop->values)
+        {
+            if (!getString(v, &val))
+            {
+                compiler->addError(ScriptCompiler::CE_INVALIDPARAMETERS, prop->file, prop->line);
+                return;
+            }
+
+            auto mergeFont = FontManager::getSingleton().getByName(val, pFont->getGroup());
+            if (!mergeFont)
+            {
+                compiler->addError(ScriptCompiler::CE_REFERENCETOANONEXISTINGOBJECT, prop->file, prop->line, val);
+                return;
+            }
+            pFont->addMergeFont(mergeFont);
+        }
+    }
     else if (attrib == "code_points")
     {
         if (prop->values.empty())

Docs/src/scripts.md

@@ -1299,4 +1299,6 @@ Here are the attributes you need to supply:
 
 @param code\_points <b>nn-nn \[nn-nn\] ..</b> This directive allows you to specify which unicode code points should be generated as glyphs into the font texture. If you don’t specify this, code points 32-126 will be generated by default which covers the ASCII glyphs. If you use this flag, you should specify a space-separated list of inclusive code point ranges of the form ’start-end’. Numbers must be decimal.
 
+@param merge_font **name [name2]** @copydetails Ogre::Font::addMergeFont
+
 You can also create new fonts at runtime by using the Ogre::FontManager if you wish.