Capture up to eight scans per submission group.

Outputs/SoftwareRendering/ScanTarget.cpp

@@ -23,5 +23,6 @@ void ScanTarget::set_modals(Modals m) {
 }
 
 void ScanTarget::submit() {
-	printf("");
+	scan_buffer_pointer_ = sample_buffer_pointer_ = 0;
+	has_failed_ = false;
 }

Outputs/SoftwareRendering/ScanTarget.hpp

@@ -28,7 +28,20 @@ class ScanTarget: public Outputs::Display::ScanTarget {
 		// some notes on their meaning to this specific scan target are given below.
 
 		void set_modals(Modals) override;
-		Scan *begin_scan() override { return &current_scan_; }
+
+		Scan *begin_scan() override {
+			if(has_failed_ || scan_buffer_pointer_ == 8) {
+				has_failed_ = true;
+				return nullptr;
+			}
+
+			vended_buffer_ = &scan_buffer_[scan_buffer_pointer_];
+			++scan_buffer_pointer_;
+			return vended_buffer_;
+		}
+		void end_scan() override {
+			// TODO: adjust sample buffer locations.
+		}
 
 		uint8_t *begin_data(size_t, size_t required_alignment) override {
 			// Achieve required alignment.
@@ -36,6 +49,8 @@ class ScanTarget: public Outputs::Display::ScanTarget {
 
 			// Return target.
 			return &sample_buffer_[sample_buffer_pointer_];
+
+			// TODO: nullptr case.
 		}
 		void end_data(size_t actual_length) override {
 			sample_buffer_pointer_ += actual_length;
@@ -46,13 +61,18 @@ class ScanTarget: public Outputs::Display::ScanTarget {
 
 		template <InputDataType, DisplayType, ColourSpace> void process();
 
-		// Temporaries; each scan is rasterised synchronously and upon
-		// completion, so the storage here is a lot simpler than for
+		// Temporaries; each set of scans is rasterised synchronously upon
+		// its submit, so the storage here is a lot simpler than for
 		// the GPU-powered scan targets.
-		Scan current_scan_;
+		std::array<Scan, 8> scan_buffer_;
+		Scan *vended_buffer_ = nullptr;
+		size_t scan_buffer_pointer_ = 0;
+
 		std::array<uint8_t, 2048> sample_buffer_;
 		size_t sample_buffer_pointer_ = 0;
 
+		bool has_failed_ = false;
+
 };
 
 }