Using manually installed SDL2 version

Game Development
1

Hello fellows. I faced some problems with the version of SDL2 (2.0.20) that I installed through apt on Ubuntu 22.04.
So following the installation instructions I installed version 2.31.0 through github. But I did so without removing the previous version.

Now, sdl2-config --version on the terminal shows that it is 2.31.0 but I think my programs are still using version 2.0.20.

Is it not advisable to install newer versions of software without first uninstalling the previous ones? Do I simply uninstall both versions and redo?
Can anyone help me out here? Thank you.

update: I uninstalled both the versions, then installed just 2.31.0. But programs still face the same problem they faced with version 2.0.20, namely: some inputs (mouse button up and down, some keys on keyboard) are being followed by the SDL_keymapchanged code. Any clues?

2

I don’t know what will happen if you have two versions installed. They will probably be installed at different locations, apt-get in /usr/lib, /usr/include, etc. and your manual install in /usr/local/lib, /usr/local/include, etc. so my guess is that you can uninstall the 2.0.20 version using apt-get without interfering with the 2.31.0 version.

1 Like
3

Did you uninstall both the “dev” package (libsdl2-dev) and the normal “runtime” package (libsdl2-2.0-0)?

You can use SDL_GetVersion to verify that you’re using the right version.

SDL_version version;
SDL_GetVersion(&version);
printf("I'm using SDL version %d.%d.%d\n", version.major, version.minor, version.patch);
1 Like
4

Thank you for your response.

I used SDL_GetVersion and the program still says version 2.0.20 eventhough I have uninstalled it. Even sdl2-config --version return 2.31.0.

Also I am using #include </usr/local/include/SDL2/SDL.h> (eventhough just <SDL2/SDL.h> was working jut fine)
Further, I checked usr/include and there is no SDL2 folder there.

what do you think?

I DID NOT uninstall the normal runtime package. Is that it?

5

Removing the runtime package fixed it. Now, the program runs on 2.31.0!
Thank you!

I just have one doubt. If you have the time…

In 2.0.20, since my program wasn’t working right, I made a simple program which just returns the event.type after SDL_PollEvent, to check exactly the problem.
with each mousebutton down, I would get 512, 1025, 772
with each mousebutton up, I would get 772, 1026, 772
some keys on the keyboard also would be wrapped in 772 (the code for SDL_KEYMAPCHANGED).

Now, that is largely fixed. Just that the mousebutton down input is still preceded by 512 (code for SDL_WINDOWEVENT).
Is this normal behaviour?

Thank you very much!

6

Which window event is it? Does it happen each time or only the first time (e.g. when the window gains focus?)

1 Like
7

I get the code 512. So I checked the SDL_Events.h file and in that is listed:

SDL_WINDOWEVENT = 0x200, /**< Window state change */

The hex translates to 512 decimal.

This happens with each mousebuttondown event. This does not happen with SDL2 v2.0.10 in my other computer.

8

There are multiple different “window events”. Look at the example on the SDL_WindowEvent wiki page.

1 Like
9

the event.window.event shows 15.
So I think SDL_WINDOWEVENT_TAKE_FOCUS.

This happens each time I click.

10

I tested this on my computers (Debian/X11, SDL 2.0.5 and SDL 2.29.2) and I don’t seem to get any SDL_WINDOWEVENT_TAKE_FOCUS events unless I click on the window borders. If I click on the title bar I get two such events each time.

I don’t fully understand how this event is meant to be used so I don’t know which behaviour is correct. You’re being “offered focus” but you already have focus so what’s the harm? It seems to be a Linux-only thing. You can probably just ignore it. I think most programs probably don’t handle this event. If you want to react to receiving focus you would use SDL_WINDOWEVENT_FOCUS_GAINED instead.

If you really are interested to know more about this event...

…here are some information that I found:

What the wiki says:

https://wiki.libsdl.org/SDL2/SDL_WindowEventID
SDL_WINDOWEVENT_TAKE_FOCUS, /**< Window is being offered a focus (should SetWindowInputFocus() on itself or a subwindow, or ignore) */

What the SDL 2.0.5 release notes said:

https://forums.libsdl.org/viewtopic.php?t=12160
Added a window event SDL_WINDOWEVENT_TAKE_FOCUS when a window manager asks the SDL window whether it wants to take focus.

You might want to read about X11’s WM_TAKE_FOCUS:
https://x.org/releases/X11R7.6/doc/xorg-docs/specs/ICCCM/icccm.html
It seems like this is where SDL gets the underlying event from which it just forwards to the application as SDL_WINDOWEVENT_TAKE_FOCUS.

1 Like
11

I swtiched from wayland to X11… and it works fine. I am crying.
Thank you for helping me :slight_smile:

some rambling, I want to vent TT -

I spent the entire day trying to get everything working after installing from source. SDL2_ttf was giving me problems. When it did work finally, I realized that the window event (which was preceding SDL_MOUSEBUTTONDOWN), was about 1 in 20 times following the SDL_MOUSEBUTTONDOWN event, REPLACING what was coming after it (sometimes even one after the other for 10 times straight).
So, a simple mouse click often did not work because it wouldn’t detect a SDL_MOUSEBUTTONUP. And I needed to check for either a mouse button up or mouse motion event after a mouse button down, so I couldn’t just assume what would come after the button down. Although I see it could have been fixed by recording the x and y coordinates on mousebuttondown, and then comparing with the coordinates of the mouse cursor after the faulty window event to figure out whether it was supposed to be a mouse click, or drag.

All this when I could have made this small change. But I did end up learning a few things. That is something.

12

I don’t think it should matter in which order you receive the SDL_MOUSEBUTTONDOWN and SDL_WINDOWEVENT_TAKE_FOCUS events.

You might get many different events for many different reasons so you cannot rely on what the previous event was.

This sounds like a much better idea.