Add ImDrawList::AddImageQuad

Adds a function
  AddImageQuad(user_texture_id, a, b, c, d, uva, uvb, uvc, uvd, col)
that shows a texture on a full quad. This allows showing arbitrary
rotations of a texture.

imgui.h

@@ -1203,6 +1203,7 @@ struct ImDrawList
     IMGUI_API void  AddText(const ImVec2& pos, ImU32 col, const char* text_begin, const char* text_end = NULL);
     IMGUI_API void  AddText(const ImFont* font, float font_size, const ImVec2& pos, ImU32 col, const char* text_begin, const char* text_end = NULL, float wrap_width = 0.0f, const ImVec4* cpu_fine_clip_rect = NULL);
     IMGUI_API void  AddImage(ImTextureID user_texture_id, const ImVec2& a, const ImVec2& b, const ImVec2& uv0 = ImVec2(0,0), const ImVec2& uv1 = ImVec2(1,1), ImU32 col = 0xFFFFFFFF);
+    IMGUI_API void  AddImageQuad(ImTextureID user_texture_id, const ImVec2& a, const ImVec2& b, const ImVec2& c, const ImVec2& d, const ImVec2& uva = ImVec2(0,0), const ImVec2& uvb = ImVec2(1,0), const ImVec2& uvc = ImVec2(1,1), const ImVec2& uvd = ImVec2(0,1), ImU32 col = 0xFFFFFFFF);
     IMGUI_API void  AddPolyline(const ImVec2* points, const int num_points, ImU32 col, bool closed, float thickness, bool anti_aliased);
     IMGUI_API void  AddConvexPolyFilled(const ImVec2* points, const int num_points, ImU32 col, bool anti_aliased);
     IMGUI_API void  AddBezierCurve(const ImVec2& pos0, const ImVec2& cp0, const ImVec2& cp1, const ImVec2& pos1, ImU32 col, float thickness, int num_segments = 0);

imgui_draw.cpp

@@ -975,6 +975,23 @@ void ImDrawList::AddImage(ImTextureID user_texture_id, const ImVec2& a, const Im
         PopTextureID();
 }
 
+void ImDrawList::AddImageQuad(ImTextureID user_texture_id, const ImVec2& a, const ImVec2& b, const ImVec2& c, const ImVec2& d, const ImVec2& uva, const ImVec2& uvb, const ImVec2& uvc, const ImVec2& uvd, ImU32 col)
+{
+    if ((col >> 24) == 0)
+        return;
+
+    // FIXME-OPT: This is wasting draw calls.
+    const bool push_texture_id = _TextureIdStack.empty() || user_texture_id != _TextureIdStack.back();
+    if (push_texture_id)
+        PushTextureID(user_texture_id);
+
+    PrimReserve(6, 4);
+    PrimQuadUV(a, b, c, d, uva, uvb, uvc, uvd, col);
+
+    if (push_texture_id)
+        PopTextureID();
+}
+
 //-----------------------------------------------------------------------------
 // ImDrawData
 //-----------------------------------------------------------------------------