Allow VRAM/GPU Loading for desktop target

[PurSnake]

Adds ability to load bitmapdata via vram :steamhappy:
But only for desktop targets

Also its part of that Funkin PR

[ACrazyTown]

Why not just use the disposeImage() method from BitmapData? I see the point of calling getTexture() as afaik it'll force a hardware texture to be created and uploaded to the GPU but this seems needlessly complex:

• BitmapData lock() and unlock() is not implemented in OpenFL: https://github.com/openfl/openfl/blob/develop/src/openfl/display/BitmapData.hx#L3120
• getTexture() checks if __texture is null, premultiplies the bitmap if needed and nulls both __surface and image: https://github.com/openfl/openfl/blob/develop/src/openfl/display/BitmapData.hx#L2252
• __surface doesn't seem to be needed as it's used with the software renderer

Maybe I'm missing something?

[EliteMasterEric]

Here's the snippet from the branch where I was experimenting with this functionality:

    trace('Uploading bitmap data to GPU... ${bitmapData?.image?.premultiplied}');

    // Retrieve the render context.
    var context:Context3D = FlxG.stage.context3D;

    // Create a new texture object using the render context.
    var texture:Texture = context.createTexture(bitmapData.width, bitmapData.height, Context3DTextureFormat.BGRA, optimizeForRender);

    // TODO: Figure out how to use texture.uploadCompressedTextureFromByteArray to save GPU memory?

    // Upload the texture to the GPU.
    // This is an expensive operation so don't do it in the UI thread if you can help it.
    texture.uploadFromBitmapData(bitmapData);

    // Now that the texture is uploaded, the `Texture` object is all we need to render it in-game.
    // We can dispose of the BitmapData object now.
    bitmapData.dispose();
    bitmapData.disposeImage();

    // Build a new, optimized BitmapData object using the Texture object.
    var output:BitmapData = BitmapData.fromTexture(texture);

    return output;

Note that this takes the bitmap data (which has already been loaded into memory from the disk), then creates a NEW texture, uploads the bitmap data to it, then creates a new BitmapData from that texture.

It looks like PurSnake's approach is trying to remove the BitmapData from the existing Bitmap so you don't have to swap to a new BitmapData like I was doing here.

[EliteMasterEric]

Also, important: It would be prudent to make the same pull request to the upstream OpenFL repository, so all users can benefit from the new feature.