vo_opengl: refactor scaler LUT weight packing/loading

This is mostly done so we can support using textures with more
components than the scaler LUTs have entries. But while we're at it,
also change the way the weights are packed so that they're always
sequential with no gaps. This allows us to simplify
pass_sample_separated_get_weights as well.

1 files changed, 8 insertions, 19 deletions

diff --git a/video/out/opengl/video_shaders.c b/video/out/opengl/video_shaders.c
index 40c5e98729..b73f13434b 100644
--- a/video/out/opengl/video_shaders.c
+++ b/video/out/opengl/video_shaders.c
@@ -41,27 +41,16 @@ static void pass_sample_separated_get_weights(struct gl_shader_cache *sc,
                                               struct scaler *scaler)
 {
     gl_sc_uniform_texture(sc, "lut", scaler->lut);
-    // Define a new variable to cache the corrected fcoord.
-    GLSLF("float fcoord_lut = LUT_POS(fcoord, %d.0);\n", scaler->lut_size);
+    GLSLF("float ypos = LUT_POS(fcoord, %d.0);\n", scaler->lut_size);
 
     int N = scaler->kernel->size;
-    if (N == 2) {
-        GLSL(vec2 c1 = texture(lut, vec2(0.5, fcoord_lut)).rg;)
-        GLSL(float weights[2] = float[](c1.r, c1.g);)
-    } else if (N == 6) {
-        GLSL(vec4 c1 = texture(lut, vec2(0.25, fcoord_lut));)
-        GLSL(vec4 c2 = texture(lut, vec2(0.75, fcoord_lut));)
-        GLSL(float weights[6] = float[](c1.r, c1.g, c1.b, c2.r, c2.g, c2.b);)
-    } else {
-        GLSLF("float weights[%d];\n", N);
-        for (int n = 0; n < N / 4; n++) {
-            GLSLF("c = texture(lut, vec2(1.0 / %d.0 + %d.0 / %d.0, fcoord_lut));\n",
-                    N / 2, n, N / 4);
-            GLSLF("weights[%d] = c.r;\n", n * 4 + 0);
-            GLSLF("weights[%d] = c.g;\n", n * 4 + 1);
-            GLSLF("weights[%d] = c.b;\n", n * 4 + 2);
-            GLSLF("weights[%d] = c.a;\n", n * 4 + 3);
-        }
+    int width = (N + 3) / 4; // round up
+
+    GLSLF("float weights[%d];\n", N);
+    for (int i = 0; i < N; i++) {
+        if (i % 4 == 0)
+            GLSLF("c = texture(lut, vec2(%f, ypos));\n", (i / 4 + 0.5) / width);
+        GLSLF("weights[%d] = c[%d];\n", i, i % 4);
     }
 }