[rcore] Add ToggleBorderlessWindowed() implementation for PLATFORM_WEB

[ghost]

Changes

1. Adds implementation for ToggleBorderlessWindowed() for PLATFORM_WEB (R214-R240).
2. Does that by first checking if it's in (any form of) browser fullscreen (R214-R215).
3. This is done with EM_ASM_INT (R214) to ensure the correct browser state, regardless internal variables or implementations.
4. If it is in fullscreen, leave fullscreen (R217) and also reset the CORE fullscreen flags (R219-R220).
5. After that, checks if FLAG_BORDERLESS_WINDOWED_MODE is set (R223).
6. If it isn't set, enters the fullscreen equivalent to Borderless Windowed (R230).
7. This was done on a short timeout to reliably handle the browser mode change delay (R228-R235).
8. It also (and also on a timeout R231-R234) sets the canvas CSS width to unset (R233), which handles the possibility of a width="value%" CSS property like on the default shell.html file.
9. This way ToggleBorderlessWindowed() can work on both a minshell.html-style or shell.html-style shell file.
10. Finally, sets the FLAG_BORDERLESS_WINDOWED_MODE (R238).
11. If the FLAG_BORDERLESS_WINDOWED_MODE was set, then just unset it (R240), since we already left fullscreen previously (R217).

Code example

• This change can be tested for PLATFORM_WEB (requires ASYNCIFY) with:

#include "raylib.h"

int main(void) {
    InitWindow(800, 450, "test");
    SetTargetFPS(60);
    while (!WindowShouldClose()) {

        if (IsKeyPressed(KEY_F)) ToggleBorderlessWindowed();

        BeginDrawing();
        ClearBackground(RAYWHITE);
        DrawText("[F] ToggleBorderlessWindowed()", 20, 20, 20, BLACK);
        EndDrawing();
    }
    CloseWindow();
    return 0;
}

Environment

• Compiled on Linux (Ubuntu 22.04 64-bit) and tested on Firefox (115.3.1esr 64-bit) and Chromium (117.0.5938.149 64-bit) for both minshell.html and shell.html files.

Edits

• 1: editting; added line marks.
• 2: formatting.

[raysan5]

@ubkp Really nice addition! Thank you very much!