A Custom Mouse Cursor

Last updated on September 21st, 2019

Any good game has a custom mouse cursor. You may think it would be a good idea to have a SDL2 surface or SDL2 texture and render it as any other sprite right at the mouse position to simulate a mouse cursor. DO NOT do this! The mouse cursor is handled separatly from the other rendering to have it smooth and working in critical situations. 

The following code shows how to set up a custom mouse cursor with SDL2 the correct way.

To have a custom mouse cursor we need a variable of type PSDL_Cursor. We call it “sdlMouseCursor” here.

The result looks like this:

Custom Mouse Cursor in SDL2
Creative Commons License This image by https://www.freepascal-meets-sdl.net is licensed under a Creative Commons Attribution 4.0 International License.
The blue cross with the yellow outline is the mouse cursor on the grey canvas/window. 

This is the interesting part of the code with regard to creating a custom mouse cursor. The cursor’s image is defined by a SDL surface. We create the SDL surface as known from a previous chapter from a png image file to “sdlSurface1” here.

The custom mouse cursor is created by the following function, which returns nil on error.

It needs the surface to use as cursor image and two coordinates (hot_x/hot_y) as arguments. They determine where the actual hitting point for this cursor is. Since the example cursor image is of dimensions 16×16 px and represents a cross, the “hot” (hitting) coordiates are (8/8), hence the cross’ center is used for hitting a button or something. In contrast you may imagine a typical arrow shaped mouse cursor, where the hitting point has to be adjusted to be right on the tip of the arrow in the arrow’s image.

If the cursor creation has been successful, it is necessary to set it to be the actual cursor. You may have created many different cursors, so tell SDL which one to use by the following procedure.

The remaining part of the code is just rendering a 500 by 500 pixels window with a grey (128, 128, 128) background that is updated as long as no mouse button has been pressed.

Finally do not forget to free the mouse cursor by SDL_FreeCursor(mouse cursor) as shown.

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