ImFont: added cpu clip fine option for ImFont::RenderChar() (which is technically internal).

(toward #7024)

imgui.h

@@ -3532,7 +3532,7 @@ struct ImFont
     // 'wrap_width' enable automatic word-wrapping across multiple lines to fit into given width. 0.0f to disable.
     IMGUI_API ImVec2            CalcTextSizeA(float size, float max_width, float wrap_width, const char* text_begin, const char* text_end = NULL, const char** remaining = NULL); // utf8
     IMGUI_API const char*       CalcWordWrapPositionA(float scale, const char* text, const char* text_end, float wrap_width);
-    IMGUI_API void              RenderChar(ImDrawList* draw_list, float size, const ImVec2& pos, ImU32 col, ImWchar c);
+    IMGUI_API void              RenderChar(ImDrawList* draw_list, float size, const ImVec2& pos, ImU32 col, ImWchar c, const ImVec4* cpu_fine_clip = NULL);
     IMGUI_API void              RenderText(ImDrawList* draw_list, float size, const ImVec2& pos, ImU32 col, const ImVec4& clip_rect, const char* text_begin, const char* text_end, float wrap_width = 0.0f, bool cpu_fine_clip = false);
 
     // [Internal] Don't use!

imgui_draw.cpp

@@ -4113,7 +4113,7 @@ ImVec2 ImFont::CalcTextSizeA(float size, float max_width, float wrap_width, cons
 }
 
 // Note: as with every ImDrawList drawing function, this expects that the font atlas texture is bound.
-void ImFont::RenderChar(ImDrawList* draw_list, float size, const ImVec2& pos, ImU32 col, ImWchar c)
+void ImFont::RenderChar(ImDrawList* draw_list, float size, const ImVec2& pos, ImU32 col, ImWchar c, const ImVec4* cpu_fine_clip)
 {
     const ImFontGlyph* glyph = FindGlyph(c);
     if (!glyph || !glyph->Visible)
@@ -4123,8 +4123,31 @@ void ImFont::RenderChar(ImDrawList* draw_list, float size, const ImVec2& pos, Im
     float scale = (size >= 0.0f) ? (size / FontSize) : 1.0f;
     float x = IM_TRUNC(pos.x);
     float y = IM_TRUNC(pos.y);
+
+    float x1 = x + glyph->X0 * scale;
+    float x2 = x + glyph->X1 * scale;
+    if (cpu_fine_clip && (x1 > cpu_fine_clip->z || x2 < cpu_fine_clip->x))
+        return;
+    float y1 = y + glyph->Y0 * scale;
+    float y2 = y + glyph->Y1 * scale;
+    float u1 = glyph->U0;
+    float v1 = glyph->V0;
+    float u2 = glyph->U1;
+    float v2 = glyph->V1;
+
+    // Always CPU fine clip. Code extracted from RenderText().
+    // CPU side clipping used to fit text in their frame when the frame is too small. Only does clipping for axis aligned quads.
+    if (cpu_fine_clip != NULL)
+    {
+        if (x1 < cpu_fine_clip->x) { u1 = u1 + (1.0f - (x2 - cpu_fine_clip->x) / (x2 - x1)) * (u2 - u1); x1 = cpu_fine_clip->x; }
+        if (y1 < cpu_fine_clip->y) { v1 = v1 + (1.0f - (y2 - cpu_fine_clip->y) / (y2 - y1)) * (v2 - v1); y1 = cpu_fine_clip->y; }
+        if (x2 > cpu_fine_clip->z) { u2 = u1 + ((cpu_fine_clip->z - x1) / (x2 - x1)) * (u2 - u1); x2 = cpu_fine_clip->z; }
+        if (y2 > cpu_fine_clip->w) { v2 = v1 + ((cpu_fine_clip->w - y1) / (y2 - y1)) * (v2 - v1); y2 = cpu_fine_clip->w; }
+        if (y1 >= y2)
+            return;
+    }
     draw_list->PrimReserve(6, 4);
-    draw_list->PrimRectUV(ImVec2(x + glyph->X0 * scale, y + glyph->Y0 * scale), ImVec2(x + glyph->X1 * scale, y + glyph->Y1 * scale), ImVec2(glyph->U0, glyph->V0), ImVec2(glyph->U1, glyph->V1), col);
+    draw_list->PrimRectUV(ImVec2(x1, y1), ImVec2(x2, y2), ImVec2(u1, v1), ImVec2(u2, v2), col);
 }
 
 // Note: as with every ImDrawList drawing function, this expects that the font atlas texture is bound.