From 06fdc50169abefbeda084d85fd011ef9c6aba735 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Sun, 24 Jun 2018 21:17:05 +1000
Subject: [PATCH] AP_OSD: switched to 2-d arrays

makes it a bit easier to read
---
 libraries/AP_OSD/AP_OSD_MAX7456.cpp | 60 +++++++++++++++--------------
 libraries/AP_OSD/AP_OSD_MAX7456.h   | 18 +++++----
 2 files changed, 41 insertions(+), 37 deletions(-)

diff --git a/libraries/AP_OSD/AP_OSD_MAX7456.cpp b/libraries/AP_OSD/AP_OSD_MAX7456.cpp
index 107df8522e..e90ed58317 100644
--- a/libraries/AP_OSD/AP_OSD_MAX7456.cpp
+++ b/libraries/AP_OSD/AP_OSD_MAX7456.cpp
@@ -136,7 +136,7 @@ AP_OSD_MAX7456::AP_OSD_MAX7456(AP_OSD &osd, AP_HAL::OwnPtr<AP_HAL::Device> dev):
     AP_OSD_Backend(osd), _dev(std::move(dev))
 {
     video_signal_reg = VIDEO_MODE_PAL | OSD_ENABLE;
-    max_screen_size = video_buffer_chars_pal;
+    video_lines = video_lines_pal;
 }
 
 bool AP_OSD_MAX7456::init()
@@ -269,10 +269,10 @@ void AP_OSD_MAX7456::reinit()
     _dev->read_registers(MAX7456ADD_STAT, &sense, 1);
     if (VIN_IS_PAL(sense)) {
         video_signal_reg = VIDEO_MODE_PAL | OSD_ENABLE;
-        max_screen_size = video_buffer_chars_pal;
+        video_lines = video_lines_pal;
     } else {
         video_signal_reg = VIDEO_MODE_NTSC | OSD_ENABLE;
-        max_screen_size = video_buffer_chars_ntsc;
+        video_lines = video_lines_ntsc;
     }
 
     // set all rows to same character black/white level
@@ -286,8 +286,8 @@ void AP_OSD_MAX7456::reinit()
     _dev->write_register(MAX7456ADD_DMM, DMM_CLEAR_DISPLAY);
 
     // force redrawing all screen
-    memset(shadow_frame, 0xFF, video_buffer_chars_pal);
-    memset(shadow_attr, 0xFF, video_buffer_chars_pal);
+    memset(shadow_frame, 0xFF, sizeof(shadow_frame));
+    memset(shadow_attr, 0xFF, sizeof(shadow_attr));
 
     initialized = true;
 }
@@ -313,25 +313,29 @@ void AP_OSD_MAX7456::transfer_frame()
     }
 
     buffer_offset = 0;
-    for (uint16_t pos=0; pos<max_screen_size; pos++) {
-        if (frame[pos] == shadow_frame[pos] && attr[pos] == shadow_attr[pos]) {
-            continue;
-        }
-        if (++updated_chars > max_updated_chars) {
-            break;
-        }
-        shadow_frame[pos] = frame[pos];
-        shadow_attr[pos] = attr[pos];
-        uint8_t attribute = attr[pos] & (DMM_BLINK | DMM_INVERT_PIXEL_COLOR);
-        uint8_t chr = frame[pos];
-
-        if (attribute != last_attribute) {
-            buffer_add_cmd(MAX7456ADD_DMM, attribute);
-            last_attribute = attribute;
+    for (uint8_t y=0; y<video_lines; y++) {
+        for (uint8_t x=0; x<video_columns; x++) {
+            
+            if (frame[y][x] == shadow_frame[y][x] && attr[y][x] == shadow_attr[y][x]) {
+                continue;
+            }
+            if (++updated_chars > max_updated_chars) {
+                break;
+            }
+            shadow_frame[y][x] = frame[y][x];
+            shadow_attr[y][x] = attr[y][x];
+            uint8_t attribute = attr[y][x] & (DMM_BLINK | DMM_INVERT_PIXEL_COLOR);
+            uint8_t chr = frame[y][x];
+
+            if (attribute != last_attribute) {
+                buffer_add_cmd(MAX7456ADD_DMM, attribute);
+                last_attribute = attribute;
+            }
+            uint16_t pos = y * video_columns + x;
+            buffer_add_cmd(MAX7456ADD_DMAH, pos >> 8);
+            buffer_add_cmd(MAX7456ADD_DMAL, pos & 0xFF);
+            buffer_add_cmd(MAX7456ADD_DMDI, chr);
         }
-        buffer_add_cmd(MAX7456ADD_DMAH, pos >> 8);
-        buffer_add_cmd(MAX7456ADD_DMAL, pos & 0xFF);
-        buffer_add_cmd(MAX7456ADD_DMDI, chr);
     }
 
     if (buffer_offset > 0) {
@@ -343,10 +347,8 @@ void AP_OSD_MAX7456::transfer_frame()
 
 void AP_OSD_MAX7456::clear()
 {
-    for (uint16_t i=0; i<video_buffer_chars_pal; i++) {
-        frame[i] = ' ';
-        attr[i] = 0;
-    }
+    memset(frame, ' ', sizeof(frame));
+    memset(attr, 0, sizeof(attr));
 }
 
 void AP_OSD_MAX7456::write(uint8_t x, uint8_t y, const char* text, uint8_t char_attr)
@@ -355,8 +357,8 @@ void AP_OSD_MAX7456::write(uint8_t x, uint8_t y, const char* text, uint8_t char_
         return;
     }
     while ((x < VIDEO_COLUMNS) && (*text != 0)) {
-        frame[y * VIDEO_COLUMNS + x] = *text;
-        attr[y * VIDEO_COLUMNS + x] = char_attr;
+        frame[y][x] = *text;
+        attr[y][x] = char_attr;
         ++text;
         ++x;
     }
diff --git a/libraries/AP_OSD/AP_OSD_MAX7456.h b/libraries/AP_OSD/AP_OSD_MAX7456.h
index 1a8ca151cf..6595c91c69 100644
--- a/libraries/AP_OSD/AP_OSD_MAX7456.h
+++ b/libraries/AP_OSD/AP_OSD_MAX7456.h
@@ -16,6 +16,7 @@
 #pragma once
 
 #include <AP_OSD/AP_OSD_Backend.h>
+#include <AP_Common/Bitmask.h>
 
 class AP_OSD_MAX7456 : public AP_OSD_Backend {
 
@@ -55,20 +56,21 @@ private:
     uint8_t  video_signal_reg;
     bool initialized;
 
-    static const uint16_t video_buffer_chars_ntsc = 390;
-    static const uint16_t video_buffer_chars_pal = 480;
+    static const uint8_t video_lines_ntsc = 13;
+    static const uint8_t video_lines_pal = 16;
+    static const uint8_t video_columns = 30;
     static const uint8_t max_updated_chars = 64;
     static const uint16_t spi_buffer_size = ((max_updated_chars + 1) * 8);
     
-    uint8_t frame[video_buffer_chars_pal];
+    uint8_t frame[video_lines_pal][video_columns];
 
     //frame already transfered to max
     //used to optimize number of characters updated
-    uint8_t shadow_frame[video_buffer_chars_pal];
+    uint8_t shadow_frame[video_lines_pal][video_columns];
 
-    uint8_t attr[video_buffer_chars_pal];
-
-    uint8_t shadow_attr[video_buffer_chars_pal];
+    // this assumes at most 32 columns
+    uint8_t attr[video_lines_pal][video_columns];
+    uint8_t shadow_attr[video_lines_pal][video_columns];
 
     uint8_t buffer[spi_buffer_size];
     int buffer_offset;
@@ -76,5 +78,5 @@ private:
     uint32_t last_signal_check;
     uint32_t video_detect_time;
 
-    uint16_t max_screen_size;
+    uint16_t video_lines;
 };