Add FramebufferWidget::viewportMargin.

include/math.hpp

@@ -435,14 +435,16 @@ struct Rect {
 
 inline Vec Vec::clamp(Rect bound) const {
 	return Vec(
-	         math::clamp(x, bound.pos.x, bound.pos.x + bound.size.x),
-	         math::clamp(y, bound.pos.y, bound.pos.y + bound.size.y));
+		math::clamp(x, bound.pos.x, bound.pos.x + bound.size.x),
+		math::clamp(y, bound.pos.y, bound.pos.y + bound.size.y)
+	);
 }
 
 inline Vec Vec::clampSafe(Rect bound) const {
 	return Vec(
-	         math::clampSafe(x, bound.pos.x, bound.pos.x + bound.size.x),
-	         math::clampSafe(y, bound.pos.y, bound.pos.y + bound.size.y));
+		math::clampSafe(x, bound.pos.x, bound.pos.x + bound.size.x),
+		math::clampSafe(y, bound.pos.y, bound.pos.y + bound.size.y)
+	);
 }
 
 

include/widget/FramebufferWidget.hpp

@@ -19,6 +19,10 @@ struct FramebufferWidget : Widget {
 	float oversample = 1.0;
 	/** Redraw when the world offset of the FramebufferWidget changes its fractional value. */
 	bool dirtyOnSubpixelChange = true;
+	/** If finite, the maximum size of the framebuffer is the viewport expanded by this margin.
+	The framebuffer is re-rendered when the viewport moves outside the margin.
+	*/
+	math::Vec viewportMargin = math::Vec(INFINITY, INFINITY);
 
 	FramebufferWidget();
 	~FramebufferWidget();
@@ -35,7 +39,7 @@ struct FramebufferWidget : Widget {
 	/** Re-renders the framebuffer, re-creating it if necessary.
 	Handles oversampling (if >1) by rendering to a temporary (larger) framebuffer and then downscaling it to the main persistent framebuffer.
 	*/
-	void render(math::Vec scale, math::Vec offsetF);
+	void render(math::Vec scale = math::Vec(1, 1), math::Vec offsetF = math::Vec(0, 0), math::Rect clipBox = math::Rect::inf());
 	/** Initializes the current GL context and draws children to it.
 	*/
 	virtual void drawFramebuffer();

src/Window.cpp

@@ -566,7 +566,7 @@ void Window::screenshotModules(const std::string& screenshotsDir, float zoom) {
 			fbw->step();
 
 			// Draw to framebuffer
-			fbw->render(math::Vec(zoom, zoom), math::Vec(0, 0));
+			fbw->render(math::Vec(zoom, zoom));
 
 			// Read pixels
 			nvgluBindFramebuffer(fbw->getFramebuffer());

src/widget/FramebufferWidget.cpp

@@ -23,6 +23,9 @@ struct FramebufferWidget::Internal {
 	math::Vec fbScale;
 	/** Framebuffer's subpixel offset relative to fbBox in world coordinates */
 	math::Vec fbOffsetF;
+	/** Local box where framebuffer content is valid.
+	*/
+	math::Rect fbClipBox = math::Rect::inf();
 };
 
 
@@ -100,22 +103,26 @@ void FramebufferWidget::draw(const DrawArgs& args) {
 	math::Vec offsetI = offset.floor();
 	math::Vec offsetF = offset.minus(offsetI);
 
-	// If drawing to a new subpixel location, rerender in the next frame.
+	// Re-render if drawing to a new subpixel location.
 	// Anything less than 0.1 pixels isn't noticeable.
 	math::Vec offsetFDelta = offsetF.minus(internal->fbOffsetF);
 	if (dirtyOnSubpixelChange && APP->window->fbDirtyOnSubpixelChange() && offsetFDelta.square() >= std::pow(0.1f, 2)) {
 		// DEBUG("%p dirty subpixel (%f, %f) (%f, %f)", this, VEC_ARGS(offsetF), VEC_ARGS(internal->fbOffsetF));
 		setDirty();
 	}
-	if (!scale.equals(internal->fbScale)) {
-		// If rescaled, rerender in the next frame.
+	// Re-render if rescaled.
+	else if (!scale.equals(internal->fbScale)) {
 		// DEBUG("%p dirty scale", this);
 		setDirty();
 	}
+	// Re-render if viewport is outside framebuffer's clipbox when it was rendered.
+	else if (!internal->fbClipBox.contains(args.clipBox)) {
+		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);
+		render(scale, offsetF, args.clipBox);
 	}
 
 	if (!internal->fb)
@@ -153,7 +160,7 @@ void FramebufferWidget::draw(const DrawArgs& args) {
 }
 
 
-void FramebufferWidget::render(math::Vec scale, math::Vec offsetF) {
+void FramebufferWidget::render(math::Vec scale, math::Vec offsetF, math::Rect clipBox) {
 	// In case we fail drawing the framebuffer, don't try again the next frame, so reset `dirty` here.
 	dirty = false;
 	NVGcontext* vg = APP->window->vg;
@@ -170,7 +177,13 @@ void FramebufferWidget::render(math::Vec scale, math::Vec offsetF) {
 		localBox = getVisibleChildrenBoundingBox();
 	}
 
-	// DEBUG("rendering FramebufferWidget localBox (%g %g %g %g) fbOffset (%g %g) fbScale (%g %g)", RECT_ARGS(localBox), VEC_ARGS(internal->fbOffsetF), VEC_ARGS(internal->fbScale));
+	// Intersect local box with viewport if viewportMargin is set
+	internal->fbClipBox = clipBox.grow(viewportMargin);
+	if (internal->fbClipBox.size.isFinite()) {
+		localBox = localBox.intersect(internal->fbClipBox);
+	}
+
+	// DEBUG("rendering FramebufferWidget localBox (%f, %f; %f, %f) fbOffset (%f, %f) fbScale (%f, %f)", RECT_ARGS(localBox), VEC_ARGS(internal->fbOffsetF), VEC_ARGS(internal->fbScale));
 	// Transform to world coordinates, then expand to nearest integer coordinates
 	math::Vec min = localBox.getTopLeft().mult(internal->fbScale).plus(internal->fbOffsetF).floor();
 	math::Vec max = localBox.getBottomRight().mult(internal->fbScale).plus(internal->fbOffsetF).ceil();