Transition from Gtk to SDL

[Kangaroux]

📖 Overview

This is a large issue that should be handled by several PRs.

Some of the work that is involved:

• [x] Add SDL libs to project
• [x] Remove libbass
• [x] Swap out app init code
• [x] Convert MainWindow to use SDL
• [x] Remove any lingering Gtk code or libs
• [x] Update docs

[Kangaroux]

The Cairo docs show that it's fairly easy to integrate Cairo with SDL. While the notefield could be rewritten to just use image blitting and thus not need Cairo I think it's worth keeping Cairo around as that will be really useful later on for custom UIs.

[Kangaroux]

I created an example to test SDL + Cairo, using the latest version of CairoSharp.

This uses SDL to create a new window and handle events. I grabbed the SDL_Surface for the window and used that as the target for Cairo.ImageSurface and created a Cairo.Context using that surface. Once you have the context you can do pretty much anything you want with Cairo. When you're done drawing you swap the buffer with SDL_UpdateWindowSurface().

using SDL2;

namespace CairoExample
{
    class Program
    {
        static void Main(string[] args)
        {
            SDL.SDL_Init(SDL.SDL_INIT_VIDEO);

            var win = SDL.SDL_CreateWindow("CairoExample", 0, 0, 800, 600, SDL.SDL_WindowFlags.SDL_WINDOW_SHOWN);
            Cairo.ImageSurface cairoSurface;

            unsafe
            {
                var surface = (SDL.SDL_Surface*)SDL.SDL_GetWindowSurface(win);
                cairoSurface = new Cairo.ImageSurface(
                    surface->pixels, Cairo.Format.RGB24, surface->w, surface->h, surface->pitch
                );
            }

            var ctx = new Cairo.Context(cairoSurface);
            var quit = false;
            SDL.SDL_Event e;

            while (!quit)
            {
                SDL.SDL_PollEvent(out e);

                if (e.type == SDL.SDL_EventType.SDL_QUIT)
                {
                    quit = true;
                }

                ctx.SetSourceRGB(0.2, 0.4, 0.6);
                ctx.Paint();

                ctx.SetSourceRGB(1, 1, 1);
                ctx.LineWidth = 3;

                ctx.MoveTo(0, 0);
                ctx.LineTo(800, 600);
                ctx.Stroke();

                SDL.SDL_UpdateWindowSurface(win);
            }

            SDL.SDL_DestroyWindow(win);
            SDL.SDL_Quit();
        }
    }
}

[Kangaroux]

[Kangaroux]

Interestingly the SDL_Surface for the window seems to be 32 bits (after checking surface->format) but configuring Cairo to use a 24 bit surface works just fine...