From 2b1fc6f7659f33994fc1201fabedf8c469cefa3c Mon Sep 17 00:00:00 2001 From: ocornut Date: Sun, 6 Aug 2023 20:13:05 +0200 Subject: [PATCH] Demo: Demonstrate out-of-order rendering using ImDrawListSplitter. --- docs/CHANGELOG.txt | 1 + imgui.h | 2 +- imgui_demo.cpp | 37 +++++++++++++++++++++++++++++++++++++ 3 files changed, 39 insertions(+), 1 deletion(-) diff --git a/docs/CHANGELOG.txt b/docs/CHANGELOG.txt index ad5868f3f..5eb96b358 100644 --- a/docs/CHANGELOG.txt +++ b/docs/CHANGELOG.txt @@ -48,6 +48,7 @@ Other changes: v_max=INT_MAX (#6675, #6679) [@jbarthelmes] - ImDrawList: Fixed OOB access in _CalcCircleAutoSegmentCount when passing excessively large radius to AddCircle(). (#6657, #5317) [@EggsyCRO, @jdpatdiscord] +- Demo: Demonstrate out-of-order rendering using ImDrawListSplitter. ----------------------------------------------------------------------- diff --git a/imgui.h b/imgui.h index 5d9a457c3..931a5d17e 100644 --- a/imgui.h +++ b/imgui.h @@ -2706,7 +2706,7 @@ struct ImDrawList // Advanced: Channels // - Use to split render into layers. By switching channels to can render out-of-order (e.g. submit FG primitives before BG primitives) // - Use to minimize draw calls (e.g. if going back-and-forth between multiple clipping rectangles, prefer to append into separate channels then merge at the end) - // - FIXME-OBSOLETE: This API shouldn't have been in ImDrawList in the first place! + // - This API shouldn't have been in ImDrawList in the first place! // Prefer using your own persistent instance of ImDrawListSplitter as you can stack them. // Using the ImDrawList::ChannelsXXXX you cannot stack a split over another. inline void ChannelsSplit(int count) { _Splitter.Split(this, count); } diff --git a/imgui_demo.cpp b/imgui_demo.cpp index aaedc7c97..674d3e49b 100644 --- a/imgui_demo.cpp +++ b/imgui_demo.cpp @@ -7866,6 +7866,43 @@ static void ShowExampleAppCustomRendering(bool* p_open) ImGui::EndTabItem(); } + // Demonstrate out-of-order rendering via channels splitting + // We use functions in ImDrawList as each draw list contains a convenience splitter, + // but you can also instantiate your own ImDrawListSplitter if you need to nest them. + if (ImGui::BeginTabItem("Draw Channels")) + { + ImDrawList* draw_list = ImGui::GetWindowDrawList(); + { + ImGui::Text("Blue shape is drawn first: appears in back"); + ImGui::Text("Red shape is drawn after: appears in front"); + ImVec2 p0 = ImGui::GetCursorScreenPos(); + draw_list->AddRectFilled(ImVec2(p0.x, p0.y), ImVec2(p0.x + 50, p0.y + 50), IM_COL32(0, 0, 255, 255)); // Blue + draw_list->AddRectFilled(ImVec2(p0.x + 25, p0.y + 25), ImVec2(p0.x + 75, p0.y + 75), IM_COL32(255, 0, 0, 255)); // Red + ImGui::Dummy(ImVec2(75, 75)); + } + ImGui::Separator(); + { + ImGui::Text("Blue shape is drawn first, into channel 1: appears in front"); + ImGui::Text("Red shape is drawn after, into channel 0: appears in back"); + ImVec2 p1 = ImGui::GetCursorScreenPos(); + + // Create 2 channels and draw a Blue shape THEN a Red shape. + // You can create any number of channels. Tables API use 1 channel per column in order to better batch draw calls. + draw_list->ChannelsSplit(2); + draw_list->ChannelsSetCurrent(1); + draw_list->AddRectFilled(ImVec2(p1.x, p1.y), ImVec2(p1.x + 50, p1.y + 50), IM_COL32(0, 0, 255, 255)); // Blue + draw_list->ChannelsSetCurrent(0); + draw_list->AddRectFilled(ImVec2(p1.x + 25, p1.y + 25), ImVec2(p1.x + 75, p1.y + 75), IM_COL32(255, 0, 0, 255)); // Red + + // Flatten/reorder channels. Red shape is in channel 0 and it appears below the Blue shape in channel 1. + // This works by copying draw indices only (vertices are not copied). + draw_list->ChannelsMerge(); + ImGui::Dummy(ImVec2(75, 75)); + ImGui::Text("After reordering, contents of channel 0 appears below channel 1."); + } + ImGui::EndTabItem(); + } + ImGui::EndTabBar(); }