`WindowPadding` not working with child windows

[my1e5]

Version of Dear PyGui

Version: 1.6.2 Operating System: macOS

My Issue/Question

Changing WindowPadding in the y direction doesn't seem to filter down to child windows.

To Reproduce

See the MWE below

Expected behavior

I expected changing the WindowPadding to affect both x and y directions, as it does with the main window.

Screenshots/Video

https://user-images.githubusercontent.com/10064103/175389789-02912d4b-493d-4678-9086-793f199057da.mov

Standalone, minimal, complete and verifiable example

import dearpygui.dearpygui as dpg
dpg.create_context()
SIZE = 200

texture_data = []
for i in range(0, SIZE**2):
    texture_data.append(0)
    texture_data.append(0)
    texture_data.append(0)
    texture_data.append(255 / 255)

with dpg.texture_registry():
    dpg.add_static_texture(width=SIZE, height=SIZE, default_value=texture_data, tag="texture_tag")

with dpg.window():
    with dpg.child_window(width=SIZE, height=SIZE, no_scrollbar=True, border=True):
        dpg.add_image("texture_tag", pos=(0,0))

dpg.show_style_editor()
dpg.create_viewport(width=SIZE*2, height=SIZE*2)
dpg.setup_dearpygui()
dpg.show_viewport()
dpg.start_dearpygui()
dpg.destroy_context()

[hugle]

Yes, you can have the behaviour without fixing the pos to (0, 0). If you really want to have pos=(0, 0), you can set pos after setting dpg.theme_component:

import dearpygui.dearpygui as dpg
dpg.create_context()
SIZE = 200

texture_data = []
for i in range(0, SIZE**2):
    texture_data.append(0)
    texture_data.append(0)
    texture_data.append(0)
    texture_data.append(255 / 255)

with dpg.texture_registry():
    dpg.add_static_texture(width=SIZE, height=SIZE, default_value=texture_data, tag="texture_tag")

with dpg.window():
    with dpg.child_window(width=SIZE+16, height=SIZE+16, no_scrollbar=True, border=True):
        dpg.add_image("texture_tag")  # Remove pos constrain

dpg.show_style_editor()
dpg.create_viewport(width=SIZE*2, height=SIZE*2)
dpg.setup_dearpygui()
dpg.show_viewport()
dpg.start_dearpygui()
dpg.destroy_context()

[DataExplorerUser]

WORKAROUND_AVAILABLE

[my1e5]

Looking back at this, I think the bug is actually that when you set pos=(0,0) the x coordinate is not applied properly. The y coordinate is actually faithfully set to 0, which is why changing the window padding in the y direction does not change the position of the image in the y direction. However, the image is not properly set to x=0 therefore it moves about when you change the window padding.

Regarding the workaround, it isn't perfect - of course you can remove window padding from that child window and the image can be positioned at (0,0). But there isn't a way to keep window padding (which you might want for other UI elements) but force the image to be located at (0,0). FYI, the proposal that you can set pos=(0,0) after setting the theme component doesn't work. For example this doesn't work:

def set_image_pos():
    dpg.configure_item(image, pos=(0,0))

dpg.set_frame_callback(1,set_image_pos)

The x coordinate of the image position can't be set to 0 - without removing window padding. But the y coordinate works correctly.

[bandit-masked]

I'll keep the issue open.

[my1e5]

I believe I've figured this out. It's to do with Imgui and the "default window clipping rectangle":

The default window clipping rectangle adds that spacing of WindowPadding.x*0.5f horizontally, and no clipping on the vertical axis. I made this choice in 1.0 because we tend to have a bias toward scrolling vertically, having no clipping-padding on the vertical axis tends to make it more noticeable that there's something to scroll to.

See https://github.com/ocornut/imgui/issues/3312#issuecomment-648052521

The 'fix' is to change the code in imgui.cpp as the above post explains.