refactor(engine): add shader program currently bound safety

2 files changed, 66 insertions, 42 deletions

diff --git a/engine/src/opengl/shader.rs b/engine/src/opengl/shader.rs
index 603c790..3dc308e 100644
--- a/engine/src/opengl/shader.rs
+++ b/engine/src/opengl/shader.rs
@@ -2,6 +2,7 @@ use std::ffi::CStr;
 use std::ptr::null_mut;
 
 use crate::matrix::Matrix;
+use crate::opengl::currently_bound::CurrentlyBound;
 
 #[derive(Debug)]
 pub struct Shader
@@ -151,14 +152,24 @@ impl Program
         Ok(())
     }
 
-    pub fn activate(&self)
+    pub fn activate(&self, cb: impl FnOnce(CurrentlyBound<'_, Self>))
     {
         unsafe {
             gl::UseProgram(self.program);
         }
+
+        // SAFETY: The shader program object is bound above
+        let currently_bound = unsafe { CurrentlyBound::new() };
+
+        cb(currently_bound);
     }
 
-    pub fn set_uniform_matrix_4fv(&self, name: &CStr, matrix: &Matrix<f32, 4, 4>)
+    pub fn set_uniform_matrix_4fv(
+        &self,
+        _: &CurrentlyBound<Self>,
+        name: &CStr,
+        matrix: &Matrix<f32, 4, 4>,
+    )
     {
         let uniform_location =
             unsafe { gl::GetUniformLocation(self.program, name.as_ptr().cast()) };
diff --git a/engine/src/renderer/mod.rs b/engine/src/renderer/mod.rs
index cad4deb..7d5e104 100644
--- a/engine/src/renderer/mod.rs
+++ b/engine/src/renderer/mod.rs
@@ -12,6 +12,7 @@ use crate::opengl::buffer::{
     ElementArrayKind as ElementArrayBufferKind,
     Usage as BufferUsage,
 };
+use crate::opengl::currently_bound::CurrentlyBound;
 #[cfg(feature = "debug")]
 use crate::opengl::debug::{MessageSeverity, MessageSource, MessageType};
 use crate::opengl::shader::Program as ShaderProgram;
@@ -70,37 +71,24 @@ impl Renderer
         clear_buffers(BufferClearMask::COLOR | BufferClearMask::DEPTH);
 
         for obj in objects {
-            obj.renderable().shader_program.activate();
-
-            apply_transformation_matrices(obj, &self.camera, window_size);
-
-            let draw = || {
-                obj.renderable().vertex_arr.bind(|vert_arr_curr_bound| {
-                    if let Some(index_info) = &obj.renderable().index_info {
-                        VertexArray::draw_elements(
-                            &vert_arr_curr_bound,
-                            PrimitiveKind::Triangles,
-                            0,
-                            index_info.cnt,
-                        );
+            obj.renderable()
+                .shader_program
+                .activate(|shader_program_curr_bound| {
+                    apply_transformation_matrices(
+                        obj,
+                        &self.camera,
+                        window_size,
+                        &shader_program_curr_bound,
+                    );
+
+                    if let Some(texture) = obj.texture() {
+                        texture.inner().bind(|_| {
+                            Self::draw_object(obj);
+                        });
                     } else {
-                        VertexArray::draw_arrays(
-                            &vert_arr_curr_bound,
-                            PrimitiveKind::Triangles,
-                            0,
-                            3,
-                        );
+                        Self::draw_object(obj);
                     }
                 });
-            };
-
-            if let Some(texture) = obj.texture() {
-                texture.inner().bind(|_| {
-                    draw();
-                });
-            } else {
-                draw();
-            }
         }
     }
 
@@ -136,6 +124,27 @@ impl Renderer
 
         set_debug_message_control(None, None, None, &[], MessageIdsAction::Disable);
     }
+
+    fn draw_object(obj: &Object)
+    {
+        obj.renderable().vertex_arr.bind(|vert_arr_curr_bound| {
+            if let Some(index_info) = &obj.renderable().index_info {
+                VertexArray::draw_elements(
+                    &vert_arr_curr_bound,
+                    PrimitiveKind::Triangles,
+                    0,
+                    index_info.cnt,
+                );
+            } else {
+                VertexArray::draw_arrays(
+                    &vert_arr_curr_bound,
+                    PrimitiveKind::Triangles,
+                    0,
+                    3,
+                );
+            }
+        });
+    }
 }
 
 #[derive(Debug)]
@@ -204,19 +213,22 @@ fn apply_transformation_matrices(
     object: &Object,
     camera: &Camera,
     window_size: &WindowSize,
+    shader_program_curr_bound: &CurrentlyBound<ShaderProgram>,
 )
 {
-    object
-        .renderable()
-        .shader_program
-        .set_uniform_matrix_4fv(cstr!("model"), &object.transform().as_matrix());
+    object.renderable().shader_program.set_uniform_matrix_4fv(
+        shader_program_curr_bound,
+        cstr!("model"),
+        &object.transform().as_matrix(),
+    );
 
     let view = camera.as_matrix();
 
-    object
-        .renderable()
-        .shader_program
-        .set_uniform_matrix_4fv(cstr!("view"), &view);
+    object.renderable().shader_program.set_uniform_matrix_4fv(
+        shader_program_curr_bound,
+        cstr!("view"),
+        &view,
+    );
 
     #[allow(clippy::cast_precision_loss)]
     let projection = new_perspective(
@@ -226,10 +238,11 @@ fn apply_transformation_matrices(
         0.1,
     );
 
-    object
-        .renderable()
-        .shader_program
-        .set_uniform_matrix_4fv(cstr!("projection"), &projection);
+    object.renderable().shader_program.set_uniform_matrix_4fv(
+        shader_program_curr_bound,
+        cstr!("projection"),
+        &projection,
+    );
 }
 
 #[cfg(feature = "debug")]