From 3045e850049354cd6be3d9f82ae824f023789234 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 12 Nov 2018 20:15:38 -0500
Subject: [PATCH] Ensures redraws when resizing; declines to busy wait
 otherwise.

---
 .../xcshareddata/xcschemes/Clock Signal.xcscheme    |  2 +-
 OSBindings/Mac/Clock Signal/Machine/CSMachine.mm    |  2 +-
 Outputs/OpenGL/ScanTarget.cpp                       | 13 +++++++++++--
 Outputs/OpenGL/ScanTarget.hpp                       |  3 ++-
 Outputs/OpenGL/ScanTargetGLSLFragments.cpp          | 12 ++++++------
 5 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme
index f9049689f..782b17c09 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
@@ -68,7 +68,7 @@
       </AdditionalOptions>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Release"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       enableASanStackUseAfterReturn = "YES"
diff --git a/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm b/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm
index 5a26574e3..0f1a7d7cf 100644
--- a/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm	
+++ b/OSBindings/Mac/Clock Signal/Machine/CSMachine.mm	
@@ -244,7 +244,7 @@ struct ActivityObserver: public Activity::Observer {
 }
 
 - (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty {
-	_scanTarget->draw();
+	_scanTarget->draw(onlyIfDirty ? false : true);
 //	_machine->crt_machine()->get_crt()->draw_frame((unsigned int)pixelSize.width, (unsigned int)pixelSize.height, onlyIfDirty ? true : false);
 }
 
diff --git a/Outputs/OpenGL/ScanTarget.cpp b/Outputs/OpenGL/ScanTarget.cpp
index 6a1755fa4..b1a569d13 100644
--- a/Outputs/OpenGL/ScanTarget.cpp
+++ b/Outputs/OpenGL/ScanTarget.cpp
@@ -286,8 +286,14 @@ template <typename T> void ScanTarget::submit_buffer(const T &array, GLuint targ
 	}
 }
 
-void ScanTarget::draw() {
-	glClear(GL_COLOR_BUFFER_BIT);
+void ScanTarget::draw(bool synchronous) {
+	if(fence_ != nullptr) {
+		// if the GPU is still busy, don't wait; we'll catch it next time
+		if(glClientWaitSync(fence_, GL_SYNC_FLUSH_COMMANDS_BIT, synchronous ? GL_TIMEOUT_IGNORED : 0) == GL_TIMEOUT_EXPIRED) {
+			return;
+		}
+		fence_ = nullptr;
+	}
 
 	// Grab the current read and submit pointers.
 	const auto submit_pointers = submit_pointers_.load();
@@ -358,8 +364,11 @@ void ScanTarget::draw() {
 
 	// TEST: draw all lines.
 	glBindFramebuffer(GL_FRAMEBUFFER, 0);
+	glClear(GL_COLOR_BUFFER_BIT);
 
 	glBindVertexArray(line_vertex_array_);
 	test_shader_->bind();
 	glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, GLsizei(scan_buffer_.size()));
+
+	fence_ = glFenceSync(GL_SYNC_GPU_COMMANDS_COMPLETE, 0);
 }
diff --git a/Outputs/OpenGL/ScanTarget.hpp b/Outputs/OpenGL/ScanTarget.hpp
index 1e64fdea3..2973bfa7b 100644
--- a/Outputs/OpenGL/ScanTarget.hpp
+++ b/Outputs/OpenGL/ScanTarget.hpp
@@ -27,7 +27,7 @@ class ScanTarget: public Outputs::Display::ScanTarget {
 	public:
 		ScanTarget();
 		~ScanTarget();
-		void draw();
+		void draw(bool synchronous);
 
 	private:
 		// Outputs::Display::ScanTarget overrides.
@@ -130,6 +130,7 @@ class ScanTarget: public Outputs::Display::ScanTarget {
 		void enable_vertex_attributes(ShaderType type, Shader &target);
 
 		std::unique_ptr<Shader> test_shader_;
+		GLsync fence_ = nullptr;
 };
 
 }
diff --git a/Outputs/OpenGL/ScanTargetGLSLFragments.cpp b/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
index d8fe3c505..76fc7be8d 100644
--- a/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
+++ b/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
@@ -45,8 +45,11 @@ std::string ScanTarget::glsl_globals(ShaderType type) {
 }
 
 std::string ScanTarget::glsl_default_vertex_shader(ShaderType type) {
-//	switch(type) {
-//		case ShaderType::Scan:
+	switch(type) {
+		case ShaderType::Scan:
+		return "";
+
+		case ShaderType::Line:
 		return
 			"void main(void) {"
 				"float lateral = float(gl_VertexID & 1);"
@@ -57,10 +60,7 @@ std::string ScanTarget::glsl_default_vertex_shader(ShaderType type) {
 				"vec2 eyePosition = vec2(-0.9, 0.9) + vec2(1.8, -1.8) * (centrePoint + height);"
 				"gl_Position = vec4(eyePosition, 0.0, 1.0);"
 			"}";
-
-//		case ShaderType::Line:
-//		return "";
-//	}
+	}
 }
 
 void ScanTarget::enable_vertex_attributes(ShaderType type, Shader &target) {