From abe47b6ed8aa09930dea33dd709c1e621dc335d9 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 15 Apr 2018 18:00:40 -0400
Subject: [PATCH] Makes first attempt at a stable display area. Not entirely
 successful.

---
 Machines/AppleII/Video.cpp | 71 ++++++++++++++++++++++++++++++++++++--
 Machines/AppleII/Video.hpp |  4 +++
 2 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/Machines/AppleII/Video.cpp b/Machines/AppleII/Video.cpp
index 45418760a..92209fc1f 100644
--- a/Machines/AppleII/Video.cpp
+++ b/Machines/AppleII/Video.cpp
@@ -22,16 +22,81 @@ Video::Video() :
 			"return float(texValue & 128u);"
 		"}");
 
-	// Show only the centre 80% of the TV frame.
+	// Show only the centre 75% of the TV frame.
 	crt_->set_video_signal(Outputs::CRT::VideoSignal::Composite);
-	crt_->set_visible_area(Outputs::CRT::Rect(0.1f, 0.1f, 0.8f, 0.8f));
+	crt_->set_visible_area(Outputs::CRT::Rect(0.115f, 0.115f, 0.77f, 0.77f));
 }
 
 Outputs::CRT::CRT *Video::get_crt() {
 	return crt_.get();
 }
 
-void Video::run_for(const Cycles) {
+void Video::run_for(const Cycles cycles) {
+	/*
+		Addressing scheme used throughout is that column 0 is the first column with pixels in it;
+		row 0 is the first row with pixels in it.
+
+		A frame is oriented around 65 cycles across, 262 lines down.
+	*/
+	const int first_sync_line = 220;	// A complete guess. Information needed.
+	const int first_sync_column = 49;	// Also a guess.
+
+	int int_cycles = cycles.as_int();
+	while(int_cycles) {
+		const int cycles_this_line = std::min(65 - column_, int_cycles);
+
+		if(row_ >= first_sync_line && row_ < first_sync_line + 3) {
+			crt_->output_sync(static_cast<unsigned int>(cycles_this_line) * 7);
+		} else {
+			const int ending_column = column_ + cycles_this_line;
+
+			if(column_ < 40) {
+				if(row_ < 192) {
+					if(!column_) {
+						pixel_pointer_ = crt_->allocate_write_area(40);
+					}
+
+					// TODO: actually store pixels.
+
+					if(ending_column >= 40) {
+						for(int c = 0; c < 40; ++c) {
+							pixel_pointer_[c] = 0xaa;
+						}
+						crt_->output_data(280, 7);
+					}
+				} else {
+					if(ending_column >= 40) {
+						crt_->output_blank(280);
+					}
+				}
+			}
+
+			const int first_blank_start = std::max(40, column_);
+			const int first_blank_end = std::min(first_sync_column, ending_column);
+			if(first_blank_end > first_blank_start) {
+				crt_->output_blank(static_cast<unsigned int>(first_blank_end - first_blank_start) * 7);
+			}
+
+			// TODO: colour burst.
+
+			const int sync_start = std::max(first_sync_column, column_);
+			const int sync_end = std::min(first_sync_column + 4, ending_column);
+			if(sync_end > sync_start) {
+				crt_->output_sync(static_cast<unsigned int>(sync_end - sync_start) * 7);
+			}
+
+			const int second_blank_start = std::max(first_sync_column + 4, column_);
+			if(ending_column > second_blank_start) {
+				crt_->output_blank(static_cast<unsigned int>(ending_column - second_blank_start) * 7);
+			}
+		}
+
+		int_cycles -= cycles_this_line;
+		column_ = (column_ + cycles_this_line) % 65;
+		if(!column_) {
+			row_ = (row_ + 1) % 262;
+		}
+	}
 }
 
 void Video::set_graphics_mode() {
diff --git a/Machines/AppleII/Video.hpp b/Machines/AppleII/Video.hpp
index 2a24b8769..999bc12e0 100644
--- a/Machines/AppleII/Video.hpp
+++ b/Machines/AppleII/Video.hpp
@@ -38,6 +38,10 @@ class Video {
 
 	private:
 		std::unique_ptr<Outputs::CRT::CRT> crt_;
+
+		int video_page_ = 0;
+		int row_ = 0, column_ = 0;
+		uint8_t *pixel_pointer_ = nullptr;
 };
 
 }