gpu: Encode number of textures use in every shader

Just define GSK_N_TEXTURES in every glsl file, extract that #define in
the python parser and emit a static const uint variable
"{shader_name}_n_textures" in the generated header.

gsk/gpu/shaders/generate-header.py

@@ -7,6 +7,7 @@ import os
 name = os.path.splitext(os.path.splitext(os.path.basename(sys.argv[1]))[0])[0][6:]
 var_name = "gsk_gpu_" + name.replace('-', '_')
 struct_name = "GskGpu" + name.title().replace('-', '') + "Instance"
+n_textures = -1
 filename = sys.argv[1]
 
 with open(filename) as f:
@@ -14,6 +15,10 @@ with open(filename) as f:
     matches = []
 
     for pos, line in enumerate (lines):
+        match = re.search(r"^#define GSK_N_TEXTURES ([0-9]+)$", line)
+        if match:
+            n_textures = int(match.group(1))
+
         match = re.search(r"^IN\(([0-9]+)\) ([a-z0-9]+) ([a-zA-Z0-9_]+);$", line)
         if not match:
             if re.search(r"layout.*\sin\s.*", line):
@@ -26,9 +31,16 @@ with open(filename) as f:
                         'location': int(match.group(1)),
                         'type': match.group(2)})
 
+if n_textures < 0:
+    raise Exception(f'''{filename}: GSK_N_TEXTURES not defined''')
+if n_textures > 2:
+    raise Exception(f'''{filename}: GSK_N_TEXTURES must be <= 2''')
+
 print(f'''/* This file is auto-generated; any change will not be preserved */
 #pragma once
 
+#define {var_name}_n_textures {n_textures}
+
 typedef struct _{struct_name} {struct_name};
 
 struct _{struct_name} {{''')

gsk/gpu/shaders/gskgpublendmode.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 2
+
 #include "common.glsl"
 #include "blendmode.glsl"
 

gsk/gpu/shaders/gskgpublur.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 1
+
 #include "common.glsl"
 
 /* blur radius (aka in_blur_direction) 0 is NOT supported and MUST be caught before */

gsk/gpu/shaders/gskgpuborder.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 0
+
 #include "common.glsl"
 
 PASS(0) vec2 _pos;

gsk/gpu/shaders/gskgpuboxshadow.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 0
+
 #include "common.glsl"
 
 /* blur radius (aka in_blur_direction) 0 is NOT supported and MUST be caught before */

gsk/gpu/shaders/gskgpucolor.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 0
+
 #include "common.glsl"
 
 PASS(0) vec2 _pos;

gsk/gpu/shaders/gskgpucolorize.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 1
+
 #include "common.glsl"
 
 PASS(0) vec2 _pos;

gsk/gpu/shaders/gskgpucolormatrix.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 1
+
 #include "common.glsl"
 
 PASS_FLAT(0) mat4 _color_matrix;

gsk/gpu/shaders/gskgpuconicgradient.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 0
+
 #include "common.glsl"
 
 #define VARIATION_SUPERSAMPLING ((GSK_VARIATION & (1u << 0)) == (1u << 0))

gsk/gpu/shaders/gskgpuconvert.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 1
+
 #include "common.glsl"
 
 #define VARIATION_OPACITY              (1u << 0)

gsk/gpu/shaders/gskgpucrossfade.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 2
+
 #include "common.glsl"
 
 PASS(0) vec2 _pos;

gsk/gpu/shaders/gskgpulineargradient.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 0
+
 #include "common.glsl"
 
 #define VARIATION_SUPERSAMPLING ((GSK_VARIATION & (1u << 0)) == (1u << 0))

gsk/gpu/shaders/gskgpumask.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 2
+
 #include "common.glsl"
 
 #define VARIATION_MASK_MODE GSK_VARIATION

gsk/gpu/shaders/gskgpuradialgradient.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 0
+
 #include "common.glsl"
 
 #define VARIATION_SUPERSAMPLING ((GSK_VARIATION & (1u << 0)) == (1u << 0))

gsk/gpu/shaders/gskgpuroundedcolor.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 0
+
 #include "common.glsl"
 
 PASS(0) vec2 _pos;

gsk/gpu/shaders/gskgputexture.glsl

@@ -1,3 +1,5 @@
+#define GSK_N_TEXTURES 1
+
 #include "common.glsl"
 
 PASS(0) vec2 _pos;