Text rendering can be finely clipped cpu-side on top and left axises (for #200)

imgui.cpp

@@ -526,7 +526,7 @@ static void         LogText(const ImVec2& ref_pos, const char* text, const char*
 
 static void         RenderText(ImVec2 pos, const char* text, const char* text_end = NULL, bool hide_text_after_hash = true);
 static void         RenderTextWrapped(ImVec2 pos, const char* text, const char* text_end, float wrap_width);
-static void         RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, const char* text, const char* text_end, const ImVec2* text_size_if_known, const ImVec2* clip_max = NULL, ImGuiAlign align = ImGuiAlign_Default);
+static void         RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, const char* text, const char* text_end, const ImVec2* text_size_if_known, ImGuiAlign align = ImGuiAlign_Default, const ImVec2* clip_min = NULL, const ImVec2* clip_max = NULL);
 static void         RenderFrame(ImVec2 p_min, ImVec2 p_max, ImU32 fill_col, bool border = true, float rounding = 0.0f);
 static void         RenderCollapseTriangle(ImVec2 p_min, bool opened, float scale = 1.0f, bool shadow = false);
 static void         RenderCheckMark(ImVec2 pos, ImU32 col);
@@ -2620,7 +2620,7 @@ static void RenderTextWrapped(ImVec2 pos, const char* text, const char* text_end
     }
 }
 
-static void RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, const char* text, const char* text_end, const ImVec2* text_size_if_known, const ImVec2* clip_max, ImGuiAlign align)
+static void RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, const char* text, const char* text_end, const ImVec2* text_size_if_known, ImGuiAlign align, const ImVec2* clip_min, const ImVec2* clip_max)
 {
     // Hide anything after a '##' string
     const char* text_display_end = FindTextDisplayEnd(text, text_end);
@@ -2632,10 +2632,12 @@ static void RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, cons
     ImGuiWindow* window = GetCurrentWindow();
 
     // Perform CPU side clipping for single clipped element to avoid using scissor state
-    if (!clip_max) clip_max = &pos_max;
     ImVec2 pos = pos_min;
     const ImVec2 text_size = text_size_if_known ? *text_size_if_known : ImGui::CalcTextSize(text, text_display_end, false, 0.0f);
-    const bool need_clipping = (pos.x + text_size.x >= clip_max->x) || (pos.y + text_size.y >= clip_max->y);
+
+    if (!clip_max) clip_max = &pos_max;
+    bool need_clipping = (pos.x + text_size.x >= clip_max->x) || (pos.y + text_size.y >= clip_max->y);
+    if (!clip_min) clip_min = &pos_min; else need_clipping |= (pos.x < clip_min->x) || (pos.y < clip_min->y);
 
     // Align
     if (align & ImGuiAlign_Center) pos.x = ImMax(pos.x, (pos.x + pos_max.x - text_size.x) * 0.5f);
@@ -2643,7 +2645,15 @@ static void RenderTextClipped(const ImVec2& pos_min, const ImVec2& pos_max, cons
     if (align & ImGuiAlign_VCenter) pos.y = ImMax(pos.y, (pos.y + pos_max.y - text_size.y) * 0.5f);
 
     // Render
-    window->DrawList->AddText(g.Font, g.FontSize, pos, window->Color(ImGuiCol_Text), text, text_display_end, 0.0f, need_clipping ? clip_max : NULL);
+    if (need_clipping)
+    {
+        ImVec4 fine_clip_rect(clip_min->x, clip_min->y, clip_max->x, clip_max->y);
+        window->DrawList->AddText(g.Font, g.FontSize, pos, window->Color(ImGuiCol_Text), text, text_display_end, 0.0f, &fine_clip_rect);
+    }
+    else
+    {
+        window->DrawList->AddText(g.Font, g.FontSize, pos, window->Color(ImGuiCol_Text), text, text_display_end, 0.0f, NULL);
+    }
     if (g.LogEnabled)
         LogText(pos, text, text_display_end);
 }
@@ -3888,7 +3898,7 @@ bool ImGui::Begin(const char* name, bool* p_opened, const ImVec2& size_on_first_
             if (style.WindowTitleAlign & ImGuiAlign_Center) pad_right = pad_left;
             if (pad_left) text_min.x += g.FontSize + style.ItemInnerSpacing.x;
             if (pad_right) text_max.x -= g.FontSize + style.ItemInnerSpacing.x;
-            RenderTextClipped(text_min, text_max, name, NULL, &text_size, &clip_max, style.WindowTitleAlign);
+            RenderTextClipped(text_min, text_max, name, NULL, &text_size, style.WindowTitleAlign, NULL, &clip_max);
         }
 
         // Save clipped aabb so we can access it in constant-time in FindHoveredWindow()
@@ -4874,7 +4884,7 @@ void ImGui::LabelTextV(const char* label, const char* fmt, va_list args)
     // Render
     const char* value_text_begin = &g.TempBuffer[0];
     const char* value_text_end = value_text_begin + ImFormatStringV(g.TempBuffer, IM_ARRAYSIZE(g.TempBuffer), fmt, args);
-    RenderTextClipped(value_bb.Min, value_bb.Max, value_text_begin, value_text_end, NULL, NULL, ImGuiAlign_VCenter);
+    RenderTextClipped(value_bb.Min, value_bb.Max, value_text_begin, value_text_end, NULL, ImGuiAlign_VCenter);
     RenderText(ImVec2(value_bb.Max.x + style.ItemInnerSpacing.x, value_bb.Min.y + style.FramePadding.y), label);
 }
 
@@ -4997,7 +5007,7 @@ static bool ButtonEx(const char* label, const ImVec2& size_arg = ImVec2(0,0), Im
     // Render
     const ImU32 col = window->Color((hovered && held) ? ImGuiCol_ButtonActive : hovered ? ImGuiCol_ButtonHovered : ImGuiCol_Button);
     RenderFrame(bb.Min, bb.Max, col, true, style.FrameRounding);
-    RenderTextClipped(bb.Min, bb.Max, label, NULL, &label_size, NULL, ImGuiAlign_Center | ImGuiAlign_VCenter);
+    RenderTextClipped(bb.Min, bb.Max, label, NULL, &label_size, ImGuiAlign_Center | ImGuiAlign_VCenter);
 
     // Automatically close popups
     //if (pressed && !(flags & ImGuiButtonFlags_DontClosePopups) && (window->Flags & ImGuiWindowFlags_Popup))
@@ -5842,7 +5852,7 @@ bool ImGui::SliderFloat(const char* label, float* v, float v_min, float v_max, c
     // Display value using user-provided display format so user can add prefix/suffix/decorations to the value.
     char value_buf[64];
     const char* value_buf_end = value_buf + ImFormatString(value_buf, IM_ARRAYSIZE(value_buf), display_format, *v);
-    RenderTextClipped(frame_bb.Min, frame_bb.Max, value_buf, value_buf_end, NULL, NULL, ImGuiAlign_Center|ImGuiAlign_VCenter);
+    RenderTextClipped(frame_bb.Min, frame_bb.Max, value_buf, value_buf_end, NULL, ImGuiAlign_Center|ImGuiAlign_VCenter);
 
     if (label_size.x > 0.0f)
         RenderText(ImVec2(frame_bb.Max.x + style.ItemInnerSpacing.x, frame_bb.Min.y + style.FramePadding.y), label);
@@ -5890,7 +5900,7 @@ bool ImGui::VSliderFloat(const char* label, const ImVec2& size, float* v, float
     // For the vertical slider we allow centered text to overlap the frame padding
     char value_buf[64];
     char* value_buf_end = value_buf + ImFormatString(value_buf, IM_ARRAYSIZE(value_buf), display_format, *v);
-    RenderTextClipped(ImVec2(frame_bb.Min.x, frame_bb.Min.y + style.FramePadding.y), frame_bb.Max, value_buf, value_buf_end, NULL, NULL, ImGuiAlign_Center);
+    RenderTextClipped(ImVec2(frame_bb.Min.x, frame_bb.Min.y + style.FramePadding.y), frame_bb.Max, value_buf, value_buf_end, NULL, ImGuiAlign_Center);
 
     if (label_size.x > 0.0f)
         RenderText(ImVec2(frame_bb.Max.x + style.ItemInnerSpacing.x, frame_bb.Min.y + style.FramePadding.y), label);
@@ -6145,7 +6155,7 @@ bool ImGui::DragFloat(const char* label, float *v, float v_speed, float v_min, f
     // Display value using user-provided display format so user can add prefix/suffix/decorations to the value.
     char value_buf[64];
     const char* value_buf_end = value_buf + ImFormatString(value_buf, IM_ARRAYSIZE(value_buf), display_format, *v);
-    RenderTextClipped(frame_bb.Min, frame_bb.Max, value_buf, value_buf_end, NULL, NULL, ImGuiAlign_Center|ImGuiAlign_VCenter);
+    RenderTextClipped(frame_bb.Min, frame_bb.Max, value_buf, value_buf_end, NULL, ImGuiAlign_Center|ImGuiAlign_VCenter);
 
     if (label_size.x > 0.0f)
         RenderText(ImVec2(frame_bb.Max.x + style.ItemInnerSpacing.x, inner_bb.Min.y), label);
@@ -6345,7 +6355,7 @@ static void Plot(ImGuiPlotType plot_type, const char* label, float (*values_gett
 
     // Text overlay
     if (overlay_text)
-        RenderTextClipped(ImVec2(frame_bb.Min.x, frame_bb.Min.y + style.FramePadding.y), frame_bb.Max, overlay_text, NULL, NULL, NULL, ImGuiAlign_Center);
+        RenderTextClipped(ImVec2(frame_bb.Min.x, frame_bb.Min.y + style.FramePadding.y), frame_bb.Max, overlay_text, NULL, NULL, ImGuiAlign_Center);
 
     RenderText(ImVec2(frame_bb.Max.x + style.ItemInnerSpacing.x, inner_bb.Min.y), label);
 }
@@ -8854,7 +8864,7 @@ void ImDrawList::AddCircleFilled(const ImVec2& centre, float radius, ImU32 col,
     }
 }
 
-void ImDrawList::AddText(const ImFont* font, float font_size, const ImVec2& pos, ImU32 col, const char* text_begin, const char* text_end, float wrap_width, const ImVec2* cpu_clip_max)
+void ImDrawList::AddText(const ImFont* font, float font_size, const ImVec2& pos, ImU32 col, const char* text_begin, const char* text_end, float wrap_width, const ImVec4* cpu_fine_clip_rect)
 {
     if ((col >> 24) == 0)
         return;
@@ -8872,7 +8882,15 @@ void ImDrawList::AddText(const ImFont* font, float font_size, const ImVec2& pos,
     const size_t vtx_begin = vtx_buffer.size();
     PrimReserve(vtx_count_max);
 
-    font->RenderText(font_size, pos, col, clip_rect_stack.back(), text_begin, text_end, this, wrap_width, cpu_clip_max);
+    ImVec4 clip_rect = clip_rect_stack.back();
+    if (cpu_fine_clip_rect)
+    {
+        clip_rect.x = ImMax(clip_rect.x, cpu_fine_clip_rect->x);
+        clip_rect.y = ImMax(clip_rect.y, cpu_fine_clip_rect->y);
+        clip_rect.z = ImMin(clip_rect.z, cpu_fine_clip_rect->z);
+        clip_rect.w = ImMin(clip_rect.w, cpu_fine_clip_rect->w);
+    }
+    font->RenderText(font_size, pos, col, clip_rect, text_begin, text_end, this, wrap_width, cpu_fine_clip_rect != NULL);
 
     // give back unused vertices
     vtx_buffer.resize((size_t)(vtx_write - &vtx_buffer.front()));
@@ -9939,7 +9957,7 @@ ImVec2 ImFont::CalcTextSizeW(float size, float max_width, const ImWchar* text_be
     return text_size;
 }
 
-void ImFont::RenderText(float size, ImVec2 pos, ImU32 col, const ImVec4& clip_rect_ref, const char* text_begin, const char* text_end, ImDrawList* draw_list, float wrap_width, const ImVec2* cpu_clip_max) const
+void ImFont::RenderText(float size, ImVec2 pos, ImU32 col, const ImVec4& clip_rect, const char* text_begin, const char* text_end, ImDrawList* draw_list, float wrap_width, bool cpu_fine_clip) const
 {
     if (!text_end)
         text_end = text_begin + strlen(text_begin);
@@ -9950,19 +9968,12 @@ void ImFont::RenderText(float size, ImVec2 pos, ImU32 col, const ImVec4& clip_re
     // Align to be pixel perfect
     pos.x = (float)(int)pos.x + DisplayOffset.x;
     pos.y = (float)(int)pos.y + DisplayOffset.y;
+    float x = pos.x;
+    float y = pos.y;
 
     const bool word_wrap_enabled = (wrap_width > 0.0f);
     const char* word_wrap_eol = NULL;
 
-    ImVec4 clip_rect = clip_rect_ref;
-    if (cpu_clip_max)
-    {
-        clip_rect.z = ImMin(clip_rect.z, cpu_clip_max->x);
-        clip_rect.w = ImMin(clip_rect.w, cpu_clip_max->y);
-    }
-    float x = pos.x;
-    float y = pos.y;
-
     ImDrawVert* out_vertices = draw_list->vtx_write;
 
     const char* s = text_begin;
@@ -10028,7 +10039,7 @@ void ImFont::RenderText(float size, ImVec2 pos, ImU32 col, const ImVec4& clip_re
                 // Clipping on Y is more likely
                 float y1 = (float)(y + glyph->YOffset * scale);
                 float y2 = (float)(y1 + glyph->Height * scale);
-                if (y1 <= clip_rect.w && y2 >= clip_rect.y)
+                if (y1 <= clip_rect.w && y2 >= clip_rect.y) // FIMXE-OPT: could fast-forward until next line
                 {
                     float x1 = (float)(x + glyph->XOffset * scale);
                     float x2 = (float)(x1 + glyph->Width * scale);
@@ -10040,20 +10051,28 @@ void ImFont::RenderText(float size, ImVec2 pos, ImU32 col, const ImVec4& clip_re
                         float u2 = glyph->U1;
                         float v2 = glyph->V1;
 
-                        // CPU side clipping used to fit text in their frame when the frame is too small. Only does clipping for axis aligned quad and in the "max" direction (bottom-right)
+                        // 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_clip_max)
+                        if (cpu_fine_clip)
                         {
-                            if (x2 > cpu_clip_max->x)
+                            if (x1 < clip_rect.x)
                             {
-                                const float clip_tx = (cpu_clip_max->x - x1) / (x2 - x1);
+                                u1 = u1 + (1.0f - (x2 - clip_rect.x) / (x2 - x1)) * (u2 - u1);
-                                x2 = cpu_clip_max->x;
+                                x1 = clip_rect.x;
-                                u2 = u1 + clip_tx * (u2 - u1);
                             }
-                            if (y2 > cpu_clip_max->y)
+                            if (y1 < clip_rect.y)
                             {
-                                const float clip_ty = (cpu_clip_max->y - y1) / (y2 - y1);
+                                v1 = v1 + (1.0f - (y2 - clip_rect.y) / (y2 - y1)) * (v2 - v1);
-                                y2 = cpu_clip_max->y;
+                                y1 = clip_rect.y;
-                                v2 = v1 + clip_ty * (v2 - v1);
+                            }
+                            if (x2 > clip_rect.z)
+                            {
+                                u2 = u1 + ((clip_rect.z - x1) / (x2 - x1)) * (u2 - u1);
+                                x2 = clip_rect.z;
+                            }
+                            if (y2 > clip_rect.w)
+                            {
+                                v2 = v1 + ((clip_rect.w - y1) / (y2 - y1)) * (v2 - v1);
+                                y2 = clip_rect.w;
                             }
                         }
 
@@ -10580,11 +10599,15 @@ void ImGui::ShowTestWindow(bool* opened)
 
         if (ImGui::TreeNode("Clipping"))
         {
-            static ImVec2 size(80, 20);
+            static ImVec2 size(100, 100), offset(50, 20);
-            ImGui::TextWrapped("On a per-widget basis we are occasionally clipping text if it won't fit in its frame.");
+            ImGui::TextWrapped("On a per-widget basis we are occasionally clipping text if it won't fit in its frame. Otherwise we are doing coarser clipping + passing a scissor rectangle to the renderer. The system is designed to try minimizing both execution and CPU/GPU rendering cost.");
-            ImGui::SliderFloat2("size", (float*)&size, 5.0f, 200.0f);
+            ImGui::DragFloat2("size", (float*)&size, 0.5f, 0.0f, 200.0f, "%.0f");
-            ImGui::Button("Line 1 hello\nLine 2 clip me!", size);
+            ImGui::DragFloat2("offset", (float*)&offset, 0.5f, -200, 200.0f, "%.0f");
-            ImGui::TextWrapped("Otherwise we are doing coarser clipping + passing a scissor rectangle to the renderer. The system is designed to try minimizing both execution and CPU/GPU rendering cost.");
+            ImVec2 pos = ImGui::GetCursorScreenPos();
+            ImVec4 clip_rect(pos.x, pos.y, pos.x+size.x, pos.y+size.y);
+            ImGui::GetWindowDrawList()->AddRectFilled(pos, pos+size, ImColor(90,90,120,255));
+            ImGui::GetWindowDrawList()->AddText(ImGui::GetWindowFont(), ImGui::GetWindowFontSize()*2.0f, pos+offset, ImColor(255,255,255,255), "Line 1 hello\nLine 2 clip me!", NULL, 0.0f, &clip_rect);
+            ImGui::Dummy(size);
             ImGui::TreePop();
         }
 

imgui.h

@@ -1022,7 +1022,7 @@ struct ImDrawList
     IMGUI_API void  AddCircle(const ImVec2& centre, float radius, ImU32 col, int num_segments = 12);
     IMGUI_API void  AddCircleFilled(const ImVec2& centre, float radius, ImU32 col, int num_segments = 12);
     IMGUI_API void  AddArcFast(const ImVec2& center, float radius, ImU32 col, int a_min_12, int a_max_12, bool filled = false, const ImVec2& third_point_offset = ImVec2(0,0)); // Angles in 0..12 range
-    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 ImVec2* cpu_clip_max = 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, const ImVec2& uv1, ImU32 col = 0xFFFFFFFF);
 
     // Advanced
@@ -1137,8 +1137,8 @@ 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) const; // utf8
     IMGUI_API ImVec2            CalcTextSizeW(float size, float max_width, const ImWchar* text_begin, const ImWchar* text_end, const ImWchar** remaining = NULL) const;                 // wchar
-    IMGUI_API void              RenderText(float size, ImVec2 pos, ImU32 col, const ImVec4& clip_rect, const char* text_begin, const char* text_end, ImDrawList* draw_list, float wrap_width = 0.0f, const ImVec2* cpu_clip_max = NULL) const;
     IMGUI_API const char*       CalcWordWrapPositionA(float scale, const char* text, const char* text_end, float wrap_width) const;
+    IMGUI_API void              RenderText(float size, ImVec2 pos, ImU32 col, const ImVec4& clip_rect, const char* text_begin, const char* text_end, ImDrawList* draw_list, float wrap_width = 0.0f, bool cpu_fine_clip = false) const;
 };
 
 //---- Include imgui_user.h at the end of imgui.h