add cpu usage meter under experimental settings

src/crab/common/frontend/controllers/gba_controller.cr

@@ -60,6 +60,8 @@ class GBAController < Controller
       ImGui.window("Experimental Settings", pointerof(@experimental_settings)) do
         ImGui.checkbox("Attempt waitloop detection", pointerof(@emu.cpu.attempt_waitloop_detection))
         ImGui.checkbox("Cache waitloop results", pointerof(@emu.cpu.cache_waitloop_results))
+        progress = emu.cpu.count_cycles.to_f32 / 280896_f32
+        ImGui.progress_bar(progress, ImGui::ImVec2.new(0, 0));
       end
     end
   end

src/crab/gba/cpu.cr

@@ -134,6 +134,8 @@ module GBA
       end
     end
 
+    property count_cycles = 0
+
     def tick : Nil
       unless @halted
         instr = read_instr
@@ -144,6 +146,7 @@ module GBA
           arm_execute instr
         end
         cycles, @gba.bus.cycles = @gba.bus.cycles, 0
+        @count_cycles += cycles
         if @entered_waitloop
           @gba.scheduler.fast_forward
           @entered_waitloop = false

src/crab/gba/gba.cr

@@ -49,6 +49,7 @@ module GBA
     end
 
     def run_until_frame : Nil
+      cpu.count_cycles = 0
       until ppu.frame
         cpu.tick
       end