Fix a bug where intermediate phase outputs could get too low height.

Basically our aspect ratio adjustment and lack of proper roundoff
could conspire to let e.g. mix(1280x720, 939x939) = 1669x938,
which is obviously wrong. I could probably have fixed it with
an extra lrintf(), but it seems more robust to simply avoid the
extra conversion (ie., never convert height -> width -> height).

Add a unit test to verify.

effect_chain.cpp

@@ -571,16 +571,30 @@ void EffectChain::output_dot_edge(FILE *fp,
 	}
 }
 
-unsigned EffectChain::fit_rectangle_to_aspect(unsigned width, unsigned height)
+void EffectChain::size_rectangle_to_fit(unsigned width, unsigned height, unsigned *output_width, unsigned *output_height)
 {
+	unsigned scaled_width, scaled_height;
+
 	if (float(width) * aspect_denom >= float(height) * aspect_nom) {
 		// Same aspect, or W/H > aspect (image is wider than the frame).
-		// In either case, keep width.
-		return width;
+		// In either case, keep width, and adjust height.
+		scaled_width = width;
+		scaled_height = lrintf(width * aspect_denom / aspect_nom);
 	} else {
 		// W/H < aspect (image is taller than the frame), so keep height,
-		// and adjust width correspondingly.
-		return lrintf(height * aspect_nom / aspect_denom);
+		// and adjust width.
+		scaled_width = lrintf(height * aspect_nom / aspect_denom);
+		scaled_height = height;
+	}
+
+	// We should be consistently larger or smaller then the existing choice,
+	// since we have the same aspect.
+	assert(!(scaled_width < *output_width && scaled_height > *output_height));
+	assert(!(scaled_height < *output_height && scaled_width > *output_width));
+
+	if (scaled_width >= *output_width && scaled_height >= *output_height) {
+		*output_width = scaled_width;
+		*output_height = scaled_height;
 	}
 }
 
@@ -652,17 +666,15 @@ void EffectChain::find_output_size(Phase *phase)
 		return;
 	}
 
+	unsigned output_width = 0, output_height = 0;
+
 	// If not, look at the input phases and textures.
 	// We select the largest one (by fit into the current aspect).
-	unsigned best_width = 0;
 	for (unsigned i = 0; i < phase->inputs.size(); ++i) {
 		Node *input = phase->inputs[i];
 		assert(input->phase->output_width != 0);
 		assert(input->phase->output_height != 0);
-		unsigned width = fit_rectangle_to_aspect(input->phase->output_width, input->phase->output_height);
-		if (width > best_width) {
-			best_width = width;
-		}
+		size_rectangle_to_fit(input->phase->output_width, input->phase->output_height, &output_width, &output_height);
 	}
 	for (unsigned i = 0; i < phase->effects.size(); ++i) {
 		Effect *effect = phase->effects[i]->effect;
@@ -671,14 +683,12 @@ void EffectChain::find_output_size(Phase *phase)
 		}
 
 		Input *input = static_cast<Input *>(effect);
-		unsigned width = fit_rectangle_to_aspect(input->get_width(), input->get_height());
-		if (width > best_width) {
-			best_width = width;
-		}
+		size_rectangle_to_fit(input->get_width(), input->get_height(), &output_width, &output_height);
 	}
-	assert(best_width != 0);
-	phase->output_width = best_width;
-	phase->output_height = best_width * aspect_denom / aspect_nom;
+	assert(output_width != 0);
+	assert(output_height != 0);
+	phase->output_width = output_width;
+	phase->output_height = output_height;
 }
 
 void EffectChain::sort_all_nodes_topologically()

effect_chain.h

@@ -148,9 +148,10 @@ class EffectChain {
 	void insert_node_between(Node *sender, Node *middle, Node *receiver);
 
 private:
-	// Fits a rectangle of the given size to the current aspect ratio
-	// (aspect_nom/aspect_denom) and returns the new width and height.
-	unsigned fit_rectangle_to_aspect(unsigned width, unsigned height);
+	// Make sure the output rectangle is at least large enough to hold
+	// the given input rectangle in both dimensions, and is of the
+	// current aspect ratio (aspect_nom/aspect_denom).
+	void size_rectangle_to_fit(unsigned width, unsigned height, unsigned *output_width, unsigned *output_height);
 
 	// Compute the input sizes for all inputs for all effects in a given phase,
 	// and inform the effects about the results.	

effect_chain_test.cpp

@@ -756,3 +756,62 @@ TEST(EffectChainTest, EffectUsedTwiceOnlyGetsOneColorspaceConversion) {
 	EXPECT_EQ("FlatInput", node->incoming_links[0]->effect->effect_type_id());
 	EXPECT_EQ("ColorspaceConversionEffect", node->outgoing_links[0]->effect->effect_type_id());
 }
+
+// An effect that does nothing, but requests texture bounce and stores
+// its input size.
+class SizeStoringEffect : public BouncingIdentityEffect {
+public:
+	SizeStoringEffect() : input_width(-1), input_height(-1) {}
+	virtual void inform_input_size(unsigned input_num, unsigned width, unsigned height) {
+		assert(input_num == 0);
+		input_width = width;
+		input_height = height;
+	}
+
+	int input_width, input_height;
+};
+
+TEST(EffectChainTest, AspectRatioConversion) {
+	float data1[4 * 3] = {
+		0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.0f,
+	};
+	float data2[7 * 7] = {
+		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
+		0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f,
+	};
+
+	// The right conversion here is that the 7x7 image decides the size,
+	// since it is the biggest, so everything is scaled up to 9x7
+	// (keep the height, round the width 9.333 to 9). 
+	float out_data[9 * 7];
+
+	EffectChainTester tester(NULL, 4, 3);
+
+	ImageFormat format;
+	format.color_space = COLORSPACE_sRGB;
+	format.gamma_curve = GAMMA_LINEAR;
+
+	FlatInput *input1 = new FlatInput(format, FORMAT_GRAYSCALE, GL_FLOAT, 4, 3);
+	input1->set_pixel_data(data1);
+
+	FlatInput *input2 = new FlatInput(format, FORMAT_GRAYSCALE, GL_FLOAT, 7, 7);
+	input2->set_pixel_data(data2);
+
+	SizeStoringEffect *input_store = new SizeStoringEffect();
+
+	tester.get_chain()->add_input(input1);
+	tester.get_chain()->add_input(input2);
+	tester.get_chain()->add_effect(new AddEffect(), input1, input2);
+	tester.get_chain()->add_effect(input_store);
+	tester.run(out_data, GL_RED, COLORSPACE_sRGB, GAMMA_LINEAR);
+
+	EXPECT_EQ(9, input_store->input_width);
+	EXPECT_EQ(7, input_store->input_height);
+}