Fixed issues with old GL versions ( <= 2.1 )

examples/modern_art/Cargo.toml

@@ -8,3 +8,4 @@ publish = false
 [dependencies]
 iced = { path = "../..", features = ["canvas", "tokio", "debug"] }
 rand = "0.8.5"
+env_logger = "0.9"

examples/modern_art/src/main.rs

@@ -9,6 +9,8 @@ use iced::{
 use rand::{thread_rng, Rng};
 
 fn main() -> iced::Result {
+    env_logger::builder().format_timestamp(None).init();
+
     ModernArt::run(Settings {
         antialiasing: true,
         ..Settings::default()

glow/src/shader/common/gradient.frag

@@ -1,20 +1,20 @@
 #ifdef GL_ES
-    #ifdef GL_FRAGMENT_PRECISION_HIGH
-        precision highp float;
-    #else
-        precision mediump float;
-    #endif
+#ifdef GL_FRAGMENT_PRECISION_HIGH
+precision highp float;
+#else
+precision mediump float;
+#endif
 #endif
 
 #ifdef HIGHER_THAN_300
-    layout (location = 0) out vec4 fragColor;
-    #define gl_FragColor fragColor
+layout (location = 0) out vec4 fragColor;
+#define gl_FragColor fragColor
 #endif
 
 in vec2 raw_position;
 
 uniform vec4 gradient_direction;
-uniform uint color_stops_size;
+uniform int color_stops_size;
 // GLSL does not support dynamically sized arrays without SSBOs so this is capped to 16 stops
 //stored as color(vec4) -> offset(vec4) sequentially;
 uniform vec4 color_stops[32];
@@ -28,23 +28,23 @@ void main() {
     vec2 unit = normalize(gradient_vec);
     float coord_offset = dot(unit, current_vec) / length(gradient_vec);
     //if a gradient has a start/end stop that is identical, the mesh will have a transparent fill
-    fragColor = vec4(0.0, 0.0, 0.0, 0.0);
+    gl_FragColor = vec4(0.0, 0.0, 0.0, 0.0);
 
     float min_offset = color_stops[1].x;
-    float max_offset = color_stops[color_stops_size - 1u].x;
+    float max_offset = color_stops[color_stops_size - 1].x;
 
-    for (uint i = 0u; i < color_stops_size - 2u; i += 2u) {
-        float curr_offset = color_stops[i+1u].x;
-        float next_offset = color_stops[i+3u].x;
+    for (int i = 0; i < color_stops_size - 2; i += 2) {
+        float curr_offset = color_stops[i+1].x;
+        float next_offset = color_stops[i+3].x;
 
         if (coord_offset <= min_offset) {
             //current coordinate is before the first defined offset, set it to the start color
-            fragColor = color_stops[0];
+            gl_FragColor = color_stops[0];
         }
 
         if (curr_offset <= coord_offset && coord_offset <= next_offset) {
             //current fragment is between the current offset processing & the next one, interpolate colors
-            fragColor = mix(color_stops[i], color_stops[i+2u], smoothstep(
+            gl_FragColor = mix(color_stops[i], color_stops[i+2], smoothstep(
                 curr_offset,
                 next_offset,
                 coord_offset
@@ -53,7 +53,7 @@ void main() {
 
         if (coord_offset >= max_offset) {
             //current coordinate is before the last defined offset, set it to the last color
-            fragColor = color_stops[color_stops_size - 2u];
+            gl_FragColor = color_stops[color_stops_size - 2];
         }
     }
 }

glow/src/shader/common/triangle.frag

@@ -14,5 +14,5 @@ out vec4 fragColor;
 uniform vec4 color;
 
 void main() {
-    fragColor = color;
+    gl_FragColor = color;
 }

glow/src/triangle/gradient.rs

@@ -71,14 +71,14 @@ impl Program {
                         linear.end.y,
                     );
 
-                    gl.uniform_1_u32(
+                    gl.uniform_1_i32(
                         Some(
                             &self
                                 .uniform_data
                                 .uniform_locations
                                 .color_stops_size_location,
                         ),
-                        (linear.color_stops.len() * 2) as u32,
+                        (linear.color_stops.len() * 2) as i32,
                     );
 
                     let mut stops = [0.0; 128];