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ImDrawList: Add comments on the usage of drawing channels

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ocornut 2015-08-25 16:31:20 +01:00
parent 77b82ecad7
commit 08b345efd9
1 changed files with 8 additions and 3 deletions
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11
imgui.h
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@ -1040,6 +1040,7 @@ IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT;
#endif
// Draw channels are used by the Columns API to "split" the render list into different channels while building, so items of each column can be batched together.
// You can also use them to simulate drawing layers and submit primitives in a different order than how they will be rendered.
struct ImDrawChannel
{
ImVector<ImDrawCmd> CmdBuffer;
@ -1105,12 +1106,16 @@ struct ImDrawList
inline void PathFill(ImU32 col) { AddConvexPolyFilled(_Path.Data, _Path.Size, col, true); PathClear(); }
inline void PathStroke(ImU32 col, bool closed, float thickness = 1.0f) { AddPolyline(_Path.Data, _Path.Size, col, closed, thickness, true); PathClear(); }
// Channels
// - Use to simulate layers. By switching channels to can render out-of-order (e.g. submit foreground primitives before background primitives)
// - Use to minimize draw calls (e.g. if going back-and-forth between multiple non-overlapping clipping rectangles, prefer to append into separate channels then merge at the end)
IMGUI_API void ChannelsSplit(int channels_count);
IMGUI_API void ChannelsMerge();
IMGUI_API void ChannelsSetCurrent(int channel_index);
// Advanced
IMGUI_API void AddCallback(ImDrawCallback callback, void* callback_data); // Your rendering function must check for 'UserCallback' in ImDrawCmd and call the function instead of rendering triangles.
IMGUI_API void AddDrawCmd(); // This is useful if you need to forcefully create a new draw call (to allow for dependent rendering / blending). Otherwise primitives are merged into the same draw-call as much as possible
IMGUI_API void ChannelsSplit(int channels_count);
IMGUI_API void ChannelsMerge();
IMGUI_API void ChannelsSetCurrent(int idx);
// Internal helpers
// NB: all primitives needs to be reserved via PrimReserve() beforehand!