When creating a DockWidgetPluginGui, the FloatingXSize and FloatingYSize provided through the passed DockWidgetPluginGuiInfo do nothing even though the InitialDockState is set to Float. You can see this issue with the provided repro as well as with the built-in Plugin Management widget.
Download and open the reproduction file in Roblox Studio
Copy the code from the script called ReproductionPlugin in Workspace
Paste the copied code into the command bar and press enter
Observe how the newly created DockWidgetPluginGui does not match the size of the frame inside of it
Expected behavior
I expect the DockWidgetPluginGui to have the size provided by DockWidgetPluginGuiInfo’s FloatingXSize and FloatingYSize when the InitialDockState is set to Float.
It does look like FloatingXSize and FloatingYSize include the header and the borders of the widget. Which means the AbsoluteSize of the DockWidgetPluginGui won’t match FloatingXSize and FloatingYSize.
I’m not sure if it’s considered a new bug report or even a new feature request to have the AbsoluteSize of the DockWidgetPluginGui to match FloatingXSize and FloatingYSize. I personally was expecting the AbsoluteSize in the repro to be (300, 400) instead of (298, 276)