MODULE shader;

FROM tigr IMPORT TigrPtr, tigrWindow, tigrFree, tigrClosed, tigrClear,
                tigrUpdate, tigrPrint, tfont, TK_ESCAPE, tigrKeyDown,
                tigrSetPostShader, tigrSetPostFX, tigrTime;
FROM helper IMPORT tigrRGB;

CONST
    fxShader = "void fxShader(out vec4 color, in vec2 uv) {vec2 tex_size = vec2(textureSize(image, 0));vec4 c = texture(image, (floor(uv * tex_size) + 0.5 * sin(parameters.x)) / tex_size);color = c;}";

VAR
    screen          : TigrPtr;
    duration, phase : SHORTREAL;
    p               : SHORTREAL;

BEGIN
    screen := tigrWindow(320, 240, "Shady", 0);
    tigrSetPostShader(screen, fxShader, HIGH(fxShader));

    duration := 1.0;
    phase    := 0.0;

    WHILE (NOT (tigrClosed(screen) > 0)) AND (NOT (tigrKeyDown(screen, TK_ESCAPE) > 0)) DO
        phase := phase + tigrTime();
        WHILE phase > duration DO
            phase := phase - duration
        END;
        p := 6.28 * phase / duration;
        tigrSetPostFX(screen, p, 0.0, 0.0, 0.0);
        tigrClear(screen, tigrRGB(80H, 90H, 0A0H));
        tigrPrint(screen, tfont, 120, 110, tigrRGB(0FFH, 0FFH, 0FFH),
                  "Shady business");
        tigrUpdate(screen);
    END;
    tigrFree(screen);
END shader.