default window icon

[vczh]

Feel free to close it if it has been implemented.

User should be offered a way to provide the executable icon. When there is no icon assigning to GacWindow, the executable icon (if exists) will take place and display on the UI.

In Windows, user do this by compiling the application with a resource.rc, executable icon is the first icon in the list. In INativeWindow::GetIcon, if no icon is assigned, the executable icon is returned. GacUI will handle the rest to display the icon.

[roodkcab]

together should be offered a way to set application id, since gtk app main loop start before GuiMain function, some application may require unique identity based on that id.

[vczh]

GuiWindow will display the default icon from INativeWindow when GuiWindow::GetIcon returns nullptr. So if all INativeWindow instances have the same default icon, they will be displayed.

In Windows, if INativeWindow::SetIcon(nullptr) is called, GetIcon returns the default icon instead of nullptr.

I believe this is some how platform depended. It is fine if gGac offers an API or a mechanism that works for gGac.