From e3f57f80df23c4b646f5c3896b52070efb48b4bf Mon Sep 17 00:00:00 2001
From: Thomas Klaehn <thomas.klaehn@perinet.io>
Date: Fri, 17 Apr 2020 07:35:36 +0200
Subject: [PATCH] Accelerate clear screen in st7789 driver

---
 src/st7789.cc | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/st7789.cc b/src/st7789.cc
index 39bbc88..a2a4145 100644
--- a/src/st7789.cc
+++ b/src/st7789.cc
@@ -1,3 +1,4 @@
+#include <array>
 #include <cstdint>
 
 #include "st7789.h"
@@ -115,17 +116,21 @@ void St7789::send_data(uint8_t data)
 
 void St7789::clear(uint16_t Color)
 {
-    unsigned int i,j;
+    unsigned int odd = 0;
+    std::array<uint8_t, 240> line;
+    for(auto it = line.begin(); it != line.end(); ++it) {
+        if(odd % 2 == 0) {
+            *it = static_cast<uint8_t>((Color >> 8) & 0xff);
+        } else {
+            *it = static_cast<uint8_t>(Color & 0xff);
+        }
+        odd++;
+    }
 
     set_windows(0, 0, 240, 240);
     this->data_command.set();
-    for(i = 0; i < 240; i++) {
-        for(j = 0; j < 240; j++){
-            uint8_t c = (Color >> 8) & 0xff;
-            this->spi.send(&c, 1);
-            c = Color & 0xff;
-            this->spi.send(&c, 1);
-        }
+    for(unsigned int i = 0; i < 240 * 2; i++) {
+        this->spi.send(line.data(), line.size());
     }
 }