From c67a4181bbf21623a9d70b79695c9a1d1f293e9e Mon Sep 17 00:00:00 2001
From: Andrew Belt <andrewpbelt@gmail.com>
Date: Thu, 23 Dec 2021 21:44:55 -0500
Subject: [PATCH] Tweak framebuffer render-skipping algorithm to be slightly
 more aggressive to render after frame deadlines.

---
 include/window/Window.hpp        |  1 +
 src/widget/FramebufferWidget.cpp | 11 ++++++++---
 src/window/Window.cpp            |  7 +++++++
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/include/window/Window.hpp b/include/window/Window.hpp
index f22d9dc1..4f2f93ba 100644
--- a/include/window/Window.hpp
+++ b/include/window/Window.hpp
@@ -103,6 +103,7 @@ struct Window {
 	}
 
 	PRIVATE bool& fbDirtyOnSubpixelChange();
+	PRIVATE int& fbCount();
 };
 
 
diff --git a/src/widget/FramebufferWidget.cpp b/src/widget/FramebufferWidget.cpp
index 7f996d2c..7f093e34 100644
--- a/src/widget/FramebufferWidget.cpp
+++ b/src/widget/FramebufferWidget.cpp
@@ -120,9 +120,14 @@ void FramebufferWidget::draw(const DrawArgs& args) {
 		setDirty();
 	}
 
-	// It's more important to not lag the frame than to draw the framebuffer
-	if (dirty && APP->window->getFrameDurationRemaining() > 0.0) {
-		render(scale, offsetF, args.clipBox);
+	if (dirty) {
+		// Render only if there is frame time remaining (to avoid lagging frames significantly), or if it's one of the first framebuffers this frame (to avoid framebuffers from never rendering).
+		int count = ++APP->window->fbCount();
+		const int maxCount = 4;
+		const float minRemaining = -1 / 60.0;
+		if (count <= maxCount || APP->window->getFrameDurationRemaining() > minRemaining) {
+			render(scale, offsetF, args.clipBox);
+		}
 	}
 
 	if (!internal->fb)
diff --git a/src/window/Window.cpp b/src/window/Window.cpp
index 1c8b185d..30d0162e 100644
--- a/src/window/Window.cpp
+++ b/src/window/Window.cpp
@@ -100,6 +100,7 @@ struct Window::Internal {
 	std::map<std::string, std::shared_ptr<Image>> imageCache;
 
 	bool fbDirtyOnSubpixelChange = true;
+	int fbCount = 0;
 };
 
 
@@ -415,6 +416,7 @@ void Window::step() {
 	double lastFrameTime = internal->frameTime;
 	internal->frameTime = frameTime;
 	internal->lastFrameDuration = frameTime - lastFrameTime;
+	internal->fbCount = 0;
 	// DEBUG("%.2lf Hz", 1.0 / internal->lastFrameDuration);
 	// double t1 = 0.0, t2 = 0.0, t3 = 0.0, t4 = 0.0, t5 = 0.0;
 
@@ -759,6 +761,11 @@ bool& Window::fbDirtyOnSubpixelChange() {
 }
 
 
+int& Window::fbCount() {
+	return internal->fbCount;
+}
+
+
 void init() {
 	int err;