graphics: Fix backwards compatibility with integer attributes

Since a359a34, glVertexAttribIPointer was used for VertexAttribute:Byte*/Short*/etc. While it is a correct behavior, it broke backwards compatibility with glsl100 shaders receiving Byte4 vectors as vec4. This commit makes this feature opt-in: it is possible to pass Byte4 as uvec4, but only if its explicitly required.

examples/triangle_color4b.rs

@@ -60,7 +60,10 @@ impl Stage {
             &[BufferLayout::default()],
             &[
                 VertexAttribute::new("in_pos", VertexFormat::Float2),
-                VertexAttribute::new("in_color", VertexFormat::Byte4),
+                VertexAttribute {
+                    gl_pass_as_float: false,
+                    ..VertexAttribute::new("in_color", VertexFormat::Byte4)
+                },
             ],
             shader,
             PipelineParams::default(),

src/graphics.rs

@@ -236,6 +236,15 @@ pub struct VertexAttribute {
     pub name: &'static str,
     pub format: VertexFormat,
     pub buffer_index: usize,
+    /// This flag affects integer VertexFormats, Byte*, Short*, Int*
+    /// Taking Byte4 as an example:
+    /// On Metal, it might be received as either `float4` or `uint4`
+    /// On OpenGl and `gl_pass_as_float = true` shaders should receive it as `vec4`
+    /// With `gl_pass_as_float = false`, as `uvec4`
+    ///
+    /// Note that `uvec4` requires at least `150` glsl version
+    /// Before setting `gl_pass_as_float` to false, better check `context.info().has_integer_attributes()` and double check that shaders are at least `150`
+    pub gl_pass_as_float: bool,
 }
 
 impl VertexAttribute {
@@ -252,6 +261,7 @@ impl VertexAttribute {
             name,
             format,
             buffer_index,
+            gl_pass_as_float: true,
         }
     }
 }

src/graphics/gl.rs

@@ -1070,6 +1070,7 @@ impl RenderingBackend for GlContext {
             name,
             format,
             buffer_index,
+            gl_pass_as_float,
         } in attributes
         {
             let buffer_data = &mut buffer_cache
@@ -1105,6 +1106,7 @@ impl RenderingBackend for GlContext {
                         stride: buffer_data.stride,
                         buffer_index: *buffer_index,
                         divisor,
+                        gl_pass_as_float: *gl_pass_as_float,
                     };
 
                     assert!(
@@ -1332,7 +1334,9 @@ impl RenderingBackend for GlContext {
                     unsafe {
                         match attribute.type_ {
                             GL_INT | GL_UNSIGNED_INT | GL_SHORT | GL_UNSIGNED_SHORT
-                            | GL_UNSIGNED_BYTE | GL_BYTE => {
+                            | GL_UNSIGNED_BYTE | GL_BYTE
+                                if !attribute.gl_pass_as_float =>
+                            {
                                 assert!(self.has_integer_attributes());
                                 glVertexAttribIPointer(
                                     attr_index as GLuint,

src/graphics/gl/cache.rs

@@ -9,6 +9,7 @@ pub struct VertexAttributeInternal {
     pub stride: i32,
     pub buffer_index: usize,
     pub divisor: i32,
+    pub gl_pass_as_float: bool,
 }
 
 #[derive(Default, Copy, Clone)]

src/native/ios.rs

@@ -340,7 +340,10 @@ pub fn define_glk_or_mtk_view_dlg(superclass: &Class) -> *const Class {
                 d.screen_width = screen_width;
                 d.screen_height = screen_height;
             }
-            send_message(Message::Resize { width: screen_width, height: screen_height });
+            send_message(Message::Resize {
+                width: screen_width,
+                height: screen_height,
+            });
         }
 
         if let Some(ref mut event_handler) = payload.event_handler {
@@ -648,8 +651,7 @@ pub fn define_app_delegate() -> *const Class {
                                 // I hope it will work the same on the real device.
                                 if conf.platform.blocking_event_loop {
                                     msg_send_![&*view, performSelectorOnMainThread:sel!(setNeedsDisplay) withObject:nil waitUntilDone:NO];
-                                }
-                                else {
+                                } else {
                                     msg_send_![&*view, performSelectorOnMainThread:sel!(display) withObject:nil waitUntilDone:YES];
                                 }
                             }

src/native/linux_x11/keycodes.rs

@@ -165,6 +165,9 @@ pub unsafe fn translate_mouse_button(button: i32) -> MouseButton {
     };
 }
 
-pub unsafe extern "C" fn keysym_to_unicode(libxkbcommon: &mut LibXkbCommon, keysym: super::libx11::KeySym) -> i32 {
-    return (libxkbcommon.xkb_keysym_to_utf32)(keysym as u32) as i32
+pub unsafe extern "C" fn keysym_to_unicode(
+    libxkbcommon: &mut LibXkbCommon,
+    keysym: super::libx11::KeySym,
+) -> i32 {
+    return (libxkbcommon.xkb_keysym_to_utf32)(keysym as u32) as i32;
 }