imgui

Class ImGuiListClipper

java.lang.Object

imgui.ImGuiListClipper

public final class ImGuiListClipper
extends java.lang.Object

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. (Dear ImGui already clip items based on their bounds but it needs to measure text size to do so, whereas manual coarse clipping before submission makes this cost and your own data fetching/submission cost almost null)

   ImGuiListClipper clipper;
   clipper.Begin(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);
 

Generally what happens is: - Clipper lets you process the first element (DisplayStart = 0, DisplayEnd = 1) regardless of it being visible or not. - User code submit one element. - Clipper can measure the height of the first element - Clipper calculate the actual range of elements to display based on the current clipping rectangle, position the cursor before the first visible element. - User code submit visible elements. - The clipper also handles various subtleties related to keyboard/gamepad navigation, wrapping etc.

BINDING NOTICE: It's impossible to implement the same API like in the original. Method forEach(int, int, ImListClipperCallback) could be used instead.

     ImGuiListClipper.forEach(1000, new ImListClipperCallback() {
         public void accept(int index) {
             ImGui.text(String.format("line number %d", index));
         }
     });
 

Method Summary

Modifier and Type	Method and Description
static void	forEach(int itemsCount, ImListClipperCallback callback)
static void	forEach(int itemsCount, int itemsHeight, ImListClipperCallback callback)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

forEach

public static void forEach(int itemsCount,
                           ImListClipperCallback callback)

Parameters:

itemsCount - 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).

callback - action to do in iterations

forEach

public static void forEach(int itemsCount,
                           int itemsHeight,
                           ImListClipperCallback callback)

Parameters:

itemsCount - 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).

itemsHeight - Use -1.0f to be calculated automatically on first step. Otherwise pass in the distance between your items, typically GetTextLineHeightWithSpacing() or GetFrameHeightWithSpacing().

callback - action to do in iterations