调整pygame窗口的大小而不会丢失键盘状态

Question

I'm facing a problem with pygame 1.9.2 based on SDL 1.2.15: the only mean of resizing window programmatically I see is pygame.display.set_mode(...) . But when I call this method my keyboard state is reset, so all currently pressed keys and modifiers send KEYUP event, repeated keys are stopped too.

When the window is resized manually by user keyboard state is perfectly normal. The event queue is paused for the time of resizing, then VIDEORESIZE and VIDEOEXPOSE events come up and keys are still pressed, if they were so.

There are few questions:

1. Is there a way to keep normal keyboard state while resizing window?
2. If not, I would like to at least keep modifier keys but I can not just use key.set_mods() because I am unable to get the moment when user releases key.
3. At last is there a way to invoke resizing of SDL window directly?

Example program demonstrates undesired behaviour. Left and right arrows resize window to same size, yet if they are pressed, there is only one keypress. Other keys are repeated normally if held. Output is event log for everything that happens.

import pygame
import sys

# same size all the time
size = (200, 200)

pygame.init()
pygame.display.set_mode(size, pygame.RESIZABLE)

# if left or right arrow key is held nothing will happen despite this line
pygame.key.set_repeat(500, 200)

run = True
while run:
    for event in pygame.event.get():
        out = '%s\t%s'%(event.type, str(event.dict))
        if event.type == pygame.QUIT:
            pygame.display.quit()
            run = False
        if event.type == pygame.KEYDOWN:
            # mods are also reset on set_mode() call
            out += ', mods = %i' % (pygame.key.get_mods())
            if event.key == pygame.K_LEFT:
                pygame.display.set_mode(size, pygame.RESIZABLE)
            if event.key == pygame.K_RIGHT:
                pygame.display.set_mode(size, pygame.RESIZABLE)

        print(out)

    pygame.time.Clock().tick(60)

Tested on Win machine but soon will report if linux fails too.

UPD: I've been digging into source of pygame and can not see why, but the documentation bundled with sources of pygame states, that Pygame can only have a single display active at any time. Creating a new one with pygame.display.set_mode() will close the previous display Pygame can only have a single display active at any time. Creating a new one with pygame.display.set_mode() will close the previous display which implies that there is no way to resize window, only to recreate it. Seems a little strange to me.

UPD: I have changed my progam behaviour so that resize does not actually happen until user releases keyboard completely. It works well and does not break usability.

Nevertheless, it would be great to know if there exists a solution to stated problem.

Answer 1

One solution is, like self. has mentioned, to store the states of the keys so that instead of using only the events, you could ignore this particular key up event. This could, however, have one problem. If you are trying to create a key control to resize the screen, which you probably are doing, then you will also be ignoring the key up event that is real. Because this kind of control is rarely implemented, there does not seem to be any kind of clean solution, like a function to just change the screen, or one to suppress the false key events. However, you could find a way around the key event problem. There are really two viable solutions. The first one (and probably the worse of the two) is to create a way to identify the fake events, and selectively ignore the key up events. Probably the easiest way to do this is to resize the screen periodically during a fixed amount of time, so that you can expect a false keyboard event at this time, and ignore it. Here is an example of the code to block a resize every second (specifically, it assumes a screen update occurs every time the system time has an exact second value, no fractions of a second) for the a key:

import pygame
import datetime

a_keydown = False
for event in pygame.event.get():
    if item.type == pygame.KEYDOWN and item.key == pygame.K_a:
        a_keydown = True
        print "keydown event"
    if item.type == pygame.KEYUP and item.key == pygame.K_a:
        if datetime.datetime.now().time()[4] > 15:           #leaves a window of fifteen microseconds for the screen resize, this may need to be adjusted
        a_keydown = False
        print "key up event"

The better of the two solutions is not this, however. Assuming the keyup event created by set_mode exists soley in python, you could get key events from elsewhere, like pywin32 for example. Try using the win32api module, and something like the GetKeyState() function for what you need. This will give you the last known state of a key. Not quite as convenient as pythons event stream, but it may be your best solution, as pygame doesn't supply an elegant solution to this.