feat(render): style, GLSL line/text pipelines, staging batches, bitmap font

include/plot/gl/handle.hpp

@@ -1,4 +1,5 @@
 #pragma once
+#include <plot/core/color.hpp>
 #include <plot/core/status.hpp>
 #include <plot/core/types.hpp>
 #include <plot/gl/api.hpp>
@@ -103,6 +104,13 @@ class Program final : public Handle<Program> {
 
   /// Sets a two-component float uniform.
   void set_uniform(const char* name, Vec2 value) const noexcept;
+  /// Sets a four-component float uniform, e.g. the colour of a pipeline.
+  void set_uniform(const char* name, Color value) const noexcept;
+
+  /// Sets an integer uniform, e.g. a sampler's texture unit. Deliberately not
+  /// an overload of the float setter: an untyped literal such as `0` must not
+  /// turn a float uniform into a `glUniform1i` call.
+  void set_uniform_int(const char* name, i32 value) const noexcept;
 
   /// Exposed for the CRTP base.
   static void destroy(GLuint id) noexcept;