diff --git a/imgui.h b/imgui.h index 8c6ad09b..5d7833e5 100644 --- a/imgui.h +++ b/imgui.h @@ -1507,6 +1507,36 @@ struct ImGuiStorage IMGUI_API void BuildSortByKey(); }; +// Helper: Manually clip large list of items. +// If you are submitting lots of evenly spaced items and you have a random access to the list, you can perform coarse clipping based on visibility to save yourself from processing those items at all. +// The clipper calculates the range of visible items and advance the cursor to compensate for the non-visible items we have skipped. +// ImGui already clip items based on their bounds but it needs to measure text size to do so. Coarse clipping before submission makes this cost and your own data fetching/submission cost null. +// Usage: +// ImGuiListClipper clipper(1000); // we have 1000 elements, evenly spaced. +// while (clipper.Step()) +// for (int i = clipper.DisplayStart; i < clipper.DisplayEnd; i++) +// ImGui::Text("line number %d", i); +// - Step 0: the clipper let you process the first element, regardless of it being visible or not, so we can measure the element height (step skipped if we passed a known height as second arg to constructor). +// - Step 1: the clipper infer height from first element, calculate the actual range of elements to display, and position the cursor before the first element. +// - (Step 2: dummy step only required if an explicit items_height was passed to constructor or Begin() and user call Step(). Does nothing and switch to Step 3.) +// - Step 3: the clipper validate that we have reached the expected Y position (corresponding to element DisplayEnd), advance the cursor to the end of the list and then returns 'false' to end the loop. +struct ImGuiListClipper +{ + float StartPosY; + float ItemsHeight; + int ItemsCount, StepNo, DisplayStart, DisplayEnd; + + // items_count: Use -1 to ignore (you can call Begin later). Use INT_MAX if you don't know how many items you have (in which case the cursor won't be advanced in the final step). + // items_height: Use -1.0f to be calculated automatically on first step. Otherwise pass in the distance between your items, typically GetTextLineHeightWithSpacing() or GetFrameHeightWithSpacing(). + // If you don't specify an items_height, you NEED to call Step(). If you specify items_height you may call the old Begin()/End() api directly, but prefer calling Step(). + ImGuiListClipper(int items_count = -1, float items_height = -1.0f) { Begin(items_count, items_height); } // NB: Begin() initialize every fields (as we allow user to call Begin/End multiple times on a same instance if they want). + ~ImGuiListClipper() { IM_ASSERT(ItemsCount == -1); } // Assert if user forgot to call End() or Step() until false. + + IMGUI_API bool Step(); // Call until it returns false. The DisplayStart/DisplayEnd fields will be set and you can process/draw those items. + IMGUI_API void Begin(int items_count, float items_height = -1.0f); // Automatically called by constructor if you passed 'items_count' or by Step() in Step 1. + IMGUI_API void End(); // Automatically called on the last call of Step() that returns false. +}; + // Helpers macros to generate 32-bits encoded colors #ifdef IMGUI_USE_BGRA_PACKED_COLOR #define IM_COL32_R_SHIFT 16 @@ -1547,36 +1577,6 @@ struct ImColor static ImColor HSV(float h, float s, float v, float a = 1.0f) { float r,g,b; ImGui::ColorConvertHSVtoRGB(h, s, v, r, g, b); return ImColor(r,g,b,a); } }; -// Helper: Manually clip large list of items. -// If you are submitting lots of evenly spaced items and you have a random access to the list, you can perform coarse clipping based on visibility to save yourself from processing those items at all. -// The clipper calculates the range of visible items and advance the cursor to compensate for the non-visible items we have skipped. -// ImGui already clip items based on their bounds but it needs to measure text size to do so. Coarse clipping before submission makes this cost and your own data fetching/submission cost null. -// Usage: -// ImGuiListClipper clipper(1000); // we have 1000 elements, evenly spaced. -// while (clipper.Step()) -// for (int i = clipper.DisplayStart; i < clipper.DisplayEnd; i++) -// ImGui::Text("line number %d", i); -// - Step 0: the clipper let you process the first element, regardless of it being visible or not, so we can measure the element height (step skipped if we passed a known height as second arg to constructor). -// - Step 1: the clipper infer height from first element, calculate the actual range of elements to display, and position the cursor before the first element. -// - (Step 2: dummy step only required if an explicit items_height was passed to constructor or Begin() and user call Step(). Does nothing and switch to Step 3.) -// - Step 3: the clipper validate that we have reached the expected Y position (corresponding to element DisplayEnd), advance the cursor to the end of the list and then returns 'false' to end the loop. -struct ImGuiListClipper -{ - float StartPosY; - float ItemsHeight; - int ItemsCount, StepNo, DisplayStart, DisplayEnd; - - // items_count: Use -1 to ignore (you can call Begin later). Use INT_MAX if you don't know how many items you have (in which case the cursor won't be advanced in the final step). - // items_height: Use -1.0f to be calculated automatically on first step. Otherwise pass in the distance between your items, typically GetTextLineHeightWithSpacing() or GetFrameHeightWithSpacing(). - // If you don't specify an items_height, you NEED to call Step(). If you specify items_height you may call the old Begin()/End() api directly, but prefer calling Step(). - ImGuiListClipper(int items_count = -1, float items_height = -1.0f) { Begin(items_count, items_height); } // NB: Begin() initialize every fields (as we allow user to call Begin/End multiple times on a same instance if they want). - ~ImGuiListClipper() { IM_ASSERT(ItemsCount == -1); } // Assert if user forgot to call End() or Step() until false. - - IMGUI_API bool Step(); // Call until it returns false. The DisplayStart/DisplayEnd fields will be set and you can process/draw those items. - IMGUI_API void Begin(int items_count, float items_height = -1.0f); // Automatically called by constructor if you passed 'items_count' or by Step() in Step 1. - IMGUI_API void End(); // Automatically called on the last call of Step() that returns false. -}; - //----------------------------------------------------------------------------- // Draw List // Hold a series of drawing commands. The user provides a renderer for ImDrawData which essentially contains an array of ImDrawList.