Mouse module issues

Issue #10 new
sp4ztique created an issue

The mouse related functions i.e. SDL_GetMouseState(), aren't well documented for python, as in C they involve getting the mouse position via x and y pointers passed to the function, rather than just returning a tuple or using a class. I've had a lot of trouble getting this function to work, as I'm trying to use the mouse for unit movement, similar to diablo or RTS games, but even when I try and create pointers with ctypes, this function doesn't want to work. If I pass x and y as None, I can get it to return the mouse button states, but I can't seem to get the right ctypes pointer.

I'd really rather use this library than the dead pygame, but if I can't get the mouse co-ordinates I'm going to be forced to switch to pygame.

Also, sorry for posting this here, if you have somewhere you'd rather questions sent I'll happily switch to that platform.

Comments (2)

  1. Marcus von Appen repo owner

    Providing a documentation for how to use all wrapped SDL2 API parts would mean duplicating the SDL2 documentation and adjusting some parts for Python's ctypes interface, which would be (mainly) a waste of time.

    I'll add a small primer about how to deal with in/out values and pointers to the py-sdl2 documentation, though, to make it easier for newcomers.

    As a rule of thumb (use with care, exceptions ahead), you can stick to the following:

    • if the argument to the function is a pointer, into which a value has to be written, use ctypes.byref() with the matching value type.
    • if the argument to the function is a pointer, which won't be modified, you can use ctypes.POINTER or, if the argument is a struct pointer, use the argument directly in most cases.

    Find below a small example for SDL_GetMouseState.

    """Simple example for using sdl2 directly."""
    import os
    import sys
    import ctypes
    from sdl2 import *
    def run():
        window = SDL_CreateWindow(b"Hello World",
                                  SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
                                  592, 460, SDL_WINDOW_SHOWN)
        fname = os.path.join(os.path.dirname(os.path.abspath(__file__)),
                             "resources", "hello.bmp")
        image = SDL_LoadBMP(fname.encode("utf-8"))
        windowsurface = SDL_GetWindowSurface(window)
        SDL_BlitSurface(image, None, windowsurface, None)
        running = True
        event = SDL_Event()
        ct_x = ctypes.c_int(0)
        ct_y = ctypes.c_int(0)
        while running:
            while SDL_PollEvent(ctypes.byref(event)) != 0:
                if event.type == SDL_QUIT:
                    running = False
            # Get the mouse state
            buttons = SDL_GetMouseState(ctypes.byref(ct_x), ctypes.byref(ct_y))
            print("Mouse is at: (%d, %d)" % (ct_x.value, ct_y.value))
            button_state = [0, 0, 0, 0, 0]
            #               (left, right, middle, x1, x2)
            if buttons & SDL_BUTTON_LMASK:
                button_state[0] = 1
            if buttons & SDL_BUTTON_RMASK:
                button_state[1] = 1
            if buttons & SDL_BUTTON_MMASK:
                button_state[2] = 1
            if buttons & SDL_BUTTON_X1MASK:
                button_state[3] = 1
            if buttons & SDL_BUTTON_X2MASK:
                button_state[4] = 1
            print("Buttons pressed: %s" % button_state)
        return 0
    if __name__ == "__main__":
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