Fix node editor drawing when built with core profile

There are two major things in this commit.

First one is to have proper stack for projection matrices. This is
something what OpenGL specification grants to have at least 2 elements
for and what is required to have for proper editor drawing without
refactoring the way how we restore projection matrix.

Supporting this stack have following advantages:

- Our GPU stack is closer to OpenGL specs, making it easier to follow
  by other developers who are always familiar with OpenGL.

- Makes it easier to port all editors to a new API.

- Should help us getting rid of extra matrix push/pop added in
  various commits to 2.8 branch.

The new API follows the following convention:

- gpuPushMatrix/gpuPopMatrix ALWAYS deals with model view matrix
  and nothing more.

  While this name does not fully indicate that it's only model view
  matrix operator, it matches behavior of other matrix operations
  such as transform which also doesn't indicate what matrix type
  they are operating on.

- Projection matrix has dedicated calls for push/pop which are
  gpuPushProjectionMatrix/gpuPopProjectionMatrix.

1 files changed, 4 insertions, 0 deletions

diff --git a/source/blender/gpu/GPU_matrix.h b/source/blender/gpu/GPU_matrix.h
index 93bb1dd4051..749784c9a2c 100644
--- a/source/blender/gpu/GPU_matrix.h
+++ b/source/blender/gpu/GPU_matrix.h
@@ -87,6 +87,10 @@ void gpuScale2f(float x, float y);
 void gpuScale2fv(const float vec[2]);
 void gpuRotate2D(float deg);
 
+/* Projection Matrix (2D or 3D) */
+
+void gpuPushProjectionMatrix(void);
+void gpuPopProjectionMatrix(void);
 
 /* 3D Projection Matrix */