add SDL2 rendering with a simple test

drawing.py

@@ -0,0 +1,113 @@
+# fx-92 Scientifique Collège+ language interpreter: On-screen drawing
+
+from sdl2 import *
+
+class Window:
+    """
+    An SDL window with pixel scaling.
+    """
+
+    BLACK = (0, 0, 0, 255)
+    WHITE = (255, 255, 255, 255)
+
+    def __init__(self, width, height, scale):
+        self.width = width
+        self.height = height
+        self.scale = scale
+
+    def __enter__(self):
+        """
+        Enter window context: allocate and create a window.
+        """
+
+        if SDL_WasInit(SDL_INIT_VIDEO):
+            raise Exception("Cannot create two windows")
+
+        if SDL_Init(SDL_INIT_VIDEO) < 0:
+            raise Exception("Failed to initialize SDL")
+
+        # Create the window
+        self.w = SDL_CreateWindow("fx-92 Scientifique Collège+".encode(),
+            SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
+            self.width*self.scale, self.height*self.scale, SDL_WINDOW_SHOWN)
+        if self.w is None:
+            raise Exception("Failed to create window")
+
+        # Create the renderer
+        self.r = SDL_CreateRenderer(self.w, -1, SDL_RENDERER_ACCELERATED)
+        if self.r is None:
+            SDL_DestroyWindow(self.w)
+            raise Exception("Failed to create renderer")
+
+        # Create the base texture where things will be rendered at scale 1
+        self.t = SDL_CreateTexture(self.r, SDL_PIXELFORMAT_ARGB8888,
+            SDL_TEXTUREACCESS_TARGET, self.width, self.height)
+        if self.t is None:
+            SDL_DestroyRenderer(r)
+            SDL_DestroyWindow(w)
+            raise Exception("Failed to create texture")
+
+        SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, b'0')
+        SDL_SetRenderTarget(self.r, self.t)
+
+        self.clear(self.WHITE)
+        self.update()
+
+        return self
+
+    def __exit__(self, *args):
+        """
+        Exit context: close and destroy window.
+        """
+
+        if self.t is not None:
+            SDL_SetRenderTarget(self.r, None)
+            SDL_DestroyTexture(self.t)
+        if self.r is not None:
+            SDL_DestroyRenderer(self.r)
+        if self.w is not None:
+            SDL_DestroyWindow(self.w)
+
+        SDL_Quit()
+
+    def clear(self, color):
+        """Clear screen in a uniform color."""
+
+        SDL_SetRenderDrawColor(self.r, *color)
+        SDL_RenderClear(self.r)
+
+    def line(self, x1, x2, y1, y2, color):
+        """Draw a straight line."""
+
+        SDL_SetRenderDrawColor(self.r, *color)
+        SDL_RenderDrawLine(self.r, x1, x2, y1, y2)
+
+    def wait(self):
+        """Wait for the window to be closed."""
+
+        event = SDL_Event()
+        while 1:
+            SDL_WaitEvent(event)
+
+            if event.type == SDL_QUIT:
+                break
+
+            if event.type == SDL_KEYDOWN:
+                key = event.key.keysym.sym
+                if key == SDLK_s:
+                    print("Going to save the picture, probably")
+
+    def update(self):
+        """Push window contents on-screen."""
+
+        # Target the window with scaling
+        SDL_SetRenderTarget(self.r, None)
+        SDL_RenderSetScale(self.r, self.scale, self.scale)
+
+        # Push that to the screen
+        SDL_RenderCopy(self.r, self.t, None, None)
+        SDL_RenderPresent(self.r)
+
+        # Go back to the texture
+        SDL_SetRenderTarget(self.r, self.t)
+        SDL_RenderSetScale(self.r, 1, 1)

fx92.py

@@ -4,6 +4,7 @@ import sys
 
 from parser import UrlParser
 from printer import print_ast
+from drawing import Window
 
 #---
 # fx-92 SC+ interpreter
@@ -39,5 +40,11 @@ def main(argv):
 
     print_ast(ast, lang="ast")
 
+    with Window(width=96, height=32, scale=8) as w:
+        w.clear(w.WHITE)
+        w.line(1, 1, 20, 20, w.BLACK)
+        w.update()
+        w.wait()
+
 if __name__ == "__main__":
     main(sys.argv)