From 787be01e61c407937ffc3482cbaa29dd6a21885e Mon Sep 17 00:00:00 2001 From: ocornut Date: Mon, 16 May 2016 20:03:18 +0200 Subject: [PATCH] ImGuiListClipper comments (#660, #661, #662) --- imgui.h | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/imgui.h b/imgui.h index c6618c58..37621762 100644 --- a/imgui.h +++ b/imgui.h @@ -1049,16 +1049,17 @@ struct ImColor }; // Helper: Manually clip large list of items. -// If you are displaying thousands of evenly spaced items and you have a random access to the list, you can perform clipping yourself to save on CPU. -// The clipper calculates the range of visible items and advance the cursor to compensate for the non-visible items we have skipped. +// 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 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 still call Step(). Does nothing and switch to Step 3. +// - (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 {