I used the _WIN32 predefined macro so it compiles the call to Windows cod on Windows. Here’s an example:

#ifdef _WIN32
		sprintf_s(buff, sizeof(buff), "%10.6f", getElapsedTime(&s));
#else
		snprintf(buff, sizeof(buff),"%10.6f",diff(&s));
#endif

I do a similar thing with the path to SDL which is “SDL.h” on Windows but “SDL2/SDL.h” on Ubuntu. Writing code this way makes it  lot less of a hassle.

Well you might say, “Don’t many Linux distros have SDL installed so people can play games?” and the answer is yes but not the development files and headers, and that’s what this shows you how to do along with a simple program to test that you can compile and run.

You’ll also need clang or gcc installed but as you can do that with a simple sudo apt install clang, it’s hardly worth a tutorial on its own.

However you also need to install VS Code and the C/C++ extension. Go to the VS Code website, download the Linux x64 version and double click on it to install it. After that from a terminal type code and it’ll appear. You then need to select extensions (5th icon down the left hand side) and pick the Microsoft C/C++ extension and install it.

I’ve added a new tutorial on the Tutorials page How to Install SDL on Linux. That includes a link to a demo file (its just above the screenshot) containing all three source code files and four VS Code configuration files for VS Code.

This program is almost identical to the asteroids_ch25 file (it draws lots of random size and colour rectangles on screen) but has been upgraded for Clang 10 and also what looks like a bug with search paths. There’s an extra line in Tasks.json to include the path to the SDL2 header files or you’ll get a can’t find a particular SDL header error when you compile.

Building code with VS Code is easy to understand once you “get” how the Folder works. I always keep the .vscode folder in there with the four C/C++ JSON configuration files and all source for that whatever it is you are compiling.  In the screenshot below (from WinSCP), you can see the path is /home/david/Projects/Examples and it contains the .vscode folder the three source files and demo which is the compiled code.  In VS Code I opened Examples as the Folder.

The .vscode folder is greyed out because the . means it’s normally hidden.

I eventually got the Windows SDL vs TTF comparison program converted to run on Raspberry-pi, after wrestling with VS Code’s Folder. Get it wrong and you can waste hours trying to get it to compile and link. I originally set the Folder (VS Code’s way of managing projects) to the pi/Projects folder (which contained both asteroids and sdlttf folders) but eventually I sussed it and set sdlttf as my Folder.  The login user is pi and so the pi folder is my home folder. I created the Projects folder under it.

This time the home brewed print routine (print) took 28x as long as the SDL_ttf compared to 14x on Windows. I used the same text.png and font.ttf files. The times are in the Window caption and read (for those with poor contrast) sdl: 35538.574 ttf: 1235.630. These times are the microsecond times to draw the strings 100x.

Changes were fairly minimal. I changed the fopen_s to fopen (used for error logging)  and changed the paths to the two font files. The other change was in the timing which used the Linux versions of hr_time.h/.c and called the diff() function instead of GetElapsedTime().

I’ve zipped up the source file (sdlttf.c) plus timing files and JSON config files for VS Code in the sdlttf_pi.zip file and put it in the LearnConLinux repository on GitHub.

Note I created a projects folder then sdlttf under that. The paths in tasks.json reflect this. To build this you’ll need libsdl2-dev,libsdl2_image_dev and libsdl2-ttf-dev installed. I used clang version 7 (the default installed on pi when you do sudo apt install clang) but I imagine gcc should also build it without any problems.

This matches my conclusions from running the virtually identical Windows version. The sdlttf way is way faster for prerendered strings than my print routine which just blits the characters out of the font bitmap one by one.

As well as the hr_time code that I used in discussion of sdldemo SDL itself provides some other ways to time. If you are happy with millisecond level accuracy of timing, just call this function which returns an unsigned 32-bit (i.e. 0- 4 billion) giving the number of milliseconds since the SDL library was initialised.

SDL_GetTicks()

The link goes to the Wiki page on libsdl.org  for SDL_GetTicks().

As always, call it twice, once to get the start value and once to get the stop then subtract start from stop to get the elapsed time in milliseconds..

For some operations this can be easier to use. A frame is 16.666666 milliseconds so if your code runs in less than 16 milliseconds, it’s not going to cause problems. In my original Windows code, it ran is a fraction of a millisecond. Compiled C code really is fast and helped because the GPU is doing most of the donkey work!

There’s also a higher accuracy timer. This I guess is just a wrapper round the system call I call in hr_time.

Uint64 SDL_GetPerformanceCounter(void)
Which I haven’t used yet but which I guess returns a processor clock count. To measure time you need to call it twice (start and stop values as before) then divide by the frequency value returned from a call to

Uint64 SDL_GetPerformanceFrequency(void)

My computer returns a clock frequency of 3,500,000,000 clocks per second but the actual value is irrelevant just divide ((stop – start)/ frequency) to get the elapsed time in seconds.

The post Other ways to time code first appeared on Learn C Games Programming Blog.]]> 125 https://learncgames.com/sdl-on-linux/?utm_source=rss&utm_medium=rss&utm_campaign=sdl-on-linux Sun, 08 Mar 2020 00:00:53 +0000 https://learncgames.com/?p=80 In my forthcoming ebook, which is the Linux equivalent of the first one I use Visual Studio Code (VSC) as the IDE to develop along with the Microsoft C/C++ extension. I’m using the SDL2 library for fast graphics and Clang as the compiler. Thankfully Microsoft have documented most of the process of using Clang with […]

apt- cache search libsdl2

Outputs this, showing what's available.

libsdl2-2.0-0 - Simple DirectMedia Layer
libsdl2-dev - Simple DirectMedia Layer development files
libsdl2-doc - Reference manual for libsdl2
libsdl2-gfx-1.0-0 - drawing and graphical effects extension for SDL2
libsdl2-gfx-dev - development files for SDL2_gfx
libsdl2-gfx-doc - documentation files for SDL2_gfx
libsdl2-image-2.0-0 - Image loading library for Simple DirectMedia Layer 2, libraries
libsdl2-image-dev - Image loading library for Simple DirectMedia Layer 2, development files
libsdl2-mixer-2.0-0 - Mixer library for Simple DirectMedia Layer 2, libraries
libsdl2-mixer-dev - Mixer library for Simple DirectMedia Layer 2, development files
libsdl2-net-2.0-0 - Network library for Simple DirectMedia Layer 2, libraries
libsdl2-net-dev - Network library for Simple DirectMedia Layer 2, development files
libsdl2-ttf-2.0-0 - TrueType Font library for Simple DirectMedia Layer 2, libraries
libsdl2-ttf-dev - TrueType Font library for Simple DirectMedia Layer 2, development files

sudo apt-get install libsdl2-dev