GPUShader: Change shader state tracking to be part of the GPUContext

This remove the use of batch->program and replace it with batch->shader.

This will allow GL abstraction latter.

source/blender/python/gpu/gpu_py_batch.c

@@ -50,7 +50,7 @@
 
 static bool bpygpu_batch_is_program_or_error(BPyGPUBatch *self)
 {
-  if (!glIsProgram(self->batch->program)) {
+  if (!self->batch->shader) {
     PyErr_SetString(PyExc_RuntimeError, "batch does not have any program assigned to it");
     return false;
   }
@@ -227,7 +227,7 @@ static PyObject *bpygpu_Batch_draw(BPyGPUBatch *self, PyObject *args)
       return NULL;
     }
   }
-  else if (self->batch->program != GPU_shader_get_program(py_program->shader)) {
+  else if (self->batch->shader != py_program->shader) {
     GPU_batch_set_shader(self->batch, py_program->shader);
   }
 
@@ -240,7 +240,7 @@ static PyObject *bpygpu_Batch_program_use_begin(BPyGPUBatch *self)
   if (!bpygpu_batch_is_program_or_error(self)) {
     return NULL;
   }
-  GPU_batch_program_use_begin(self->batch);
+  GPU_shader_bind(self->batch->shader);
   Py_RETURN_NONE;
 }
 
@@ -249,7 +249,7 @@ static PyObject *bpygpu_Batch_program_use_end(BPyGPUBatch *self)
   if (!bpygpu_batch_is_program_or_error(self)) {
     return NULL;
   }
-  GPU_batch_program_use_end(self->batch);
+  GPU_shader_unbind();
   Py_RETURN_NONE;
 }