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. 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: empty 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.

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