Setting window position with a pivot is incorrect with collapsed window

[hiddenhare]

Version/Branch of Dear ImGui:

Version: 1.75
Branch: imgui-rs (Rust binding), version 0.4
Back-end: Custom

My Issue/Question:

I'm attempting to position a stack of windows in the bottom-left corner of the screen. I position the first window with a pivot of [0.0, 1.0] and a condition of Always. I measure that window's height, and then position my second window just above it, with the same pivot and condition.

Expected behaviour: When collapsed, the first window should reposition itself so that the bottom-left corner of its titlebar lines up with the bottom-left corner of the screen.

Observed behaviour: When collapsed, the first window retains its current position, causing it to overlap with the second window.

Example:

const PADDING: f32 = 30.0;

let window1 = Window::new(&ImString::new("Window 1"))
    .position([PADDING, screen_height - PADDING], Condition::Always)
    .position_pivot([0.0, 1.0])
    .movable(false)
    .resizable(false)
    .begin(&ui);

let mut window1_size = [0.0, 0.0];
if let Some(window1) = window1 {
    ui.text("Window 1 Contents");
    window1_size = ui.window_size();
    window1.end(&ui);
}

let window2 = Window::new(&ImString::new("Window 2"))
    .position([PADDING, screen_height - window1_size[1] - PADDING * 2.0], Condition::Always)
    .position_pivot([0.0, 1.0])
    .movable(false)
    .resizable(false)
    .begin(&ui);

if let Some(window2) = window2 {
    ui.text("Window 2 Contents");
    window2.end(&ui);
}

[ocornut]

Thank you @hiddenhare for your report.
Here's the C++ repro:

float padding = 32.0f;
ImGui::SetNextWindowPos(ImVec2(padding, ImGui::GetIO().DisplaySize.y - padding), ImGuiCond_Always, ImVec2(0.0f, 1.0f));
ImGui::Begin("Window 1", NULL, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize);
ImGui::Text("Window 1 contents");
ImVec2 window1_size = ImGui::GetWindowSize();
ImGui::End();

ImGui::SetNextWindowPos(ImVec2(padding, ImGui::GetIO().DisplaySize.y - window1_size.y - padding * 2.0f), ImGuiCond_Always, ImVec2(0.0f, 1.0f));
ImGui::Begin("Window 2", NULL, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize);
ImGui::Text("Window 2 contents");
ImGui::End();

And the bug has been fixed and pushed by 45499b8.
Will add this to our list of regression tests.