fix viewport not being set for probe draw (#2489)

game/graphics/opengl_renderer/shaders/glow_probe_downsample.frag

@@ -1,8 +1,9 @@
 #version 430 core
 
 out vec4 out_color;
+
 uniform sampler2D tex;
-in flat vec4 fragment_color;
+
 in vec2 tex_coord;
 
 void main() {

game/graphics/opengl_renderer/sprite/GlowRenderer.cpp

@@ -538,6 +538,9 @@ void GlowRenderer::draw_probes(SharedRenderState* render_state,
   glBindVertexArray(m_ogl.vao);
   glEnable(GL_PRIMITIVE_RESTART);
   glPrimitiveRestartIndex(UINT32_MAX);
+  GLint old_viewport[4];
+  glGetIntegerv(GL_VIEWPORT, old_viewport);
+  glViewport(0, 0, m_ogl.probe_fbo_w, m_ogl.probe_fbo_h);
   glBindBuffer(GL_ARRAY_BUFFER, m_ogl.vertex_buffer);
   glBufferData(GL_ARRAY_BUFFER, m_next_vertex * sizeof(Vertex), m_vertex_buffer.data(),
                GL_STREAM_DRAW);
@@ -554,6 +557,7 @@ void GlowRenderer::draw_probes(SharedRenderState* render_state,
   glDepthFunc(GL_GEQUAL);
   glDrawElements(GL_TRIANGLE_STRIP, idx_end - idx_start, GL_UNSIGNED_INT,
                  (void*)(idx_start * sizeof(u32)));
+  glViewport(old_viewport[0], old_viewport[1], old_viewport[2], old_viewport[3]);
 }
 
 /*!
@@ -744,4 +748,4 @@ u32* GlowRenderer::alloc_index(int num) {
   auto* result = &m_index_buffer[m_next_index];
   m_next_index += num;
   return result;
-}
+}