Sped up internal font drawing for opaque background color

Author: Laurence Bank

Adafruit_GFX.cpp

@@ -244,6 +244,36 @@ void Adafruit_GFX::writeFillRect(int16_t x, int16_t y, int16_t w, int16_t h,
   fillRect(x, y, w, h, color);
 }
 
+/**************************************************************************/
+/*!
+   @brief    set the address window (memory area), overwrite in subclasses if needed
+*/
+/**************************************************************************/
+void Adafruit_GFX::setAddrWindow(unsigned short x, unsigned short y, unsigned short w, unsigned short h)
+{
+  (void)x; (void)y; (void)w; (void)h;
+}
+
+/**************************************************************************/
+/*!
+   @brief    write len pixels of the given color, overwrite in subclasses if needed
+*/
+/**************************************************************************/
+void Adafruit_GFX::writeColor(uint16_t color, uint32_t len)
+{
+ (void)color; (void)len;
+}
+
+/**************************************************************************/
+/*!
+   @brief    write a buffer of pixels, overwrite in subclasses if needed
+*/
+void Adafruit_GFX::writePixels(uint16_t *colors, uint32_t len, bool block,
+                   bool bigEndian)
+{
+  (void)colors; (void)len; (void)block; (void)bigEndian;
+}
+
 /**************************************************************************/
 /*!
    @brief    End a display-writing routine, overwrite in subclasses if
@@ -1147,28 +1177,41 @@ void Adafruit_GFX::drawChar(int16_t x, int16_t y, unsigned char c,
       c++; // Handle 'classic' charset behavior
 
     startWrite();
-    for (int8_t i = 0; i < 5; i++) { // Char bitmap = 5 columns
-      uint8_t line = pgm_read_byte(&font[c * 5 + i]);
-      for (int8_t j = 0; j < 8; j++, line >>= 1) {
-        if (line & 1) {
-          if (size_x == 1 && size_y == 1)
-            writePixel(x + i, y + j, color);
-          else
-            writeFillRect(x + i * size_x, y + j * size_y, size_x, size_y,
+      if (color != bg) { // faster opaque text
+        setAddrWindow(x, y, 5*size_x, 7*size_y);
+        for (int8_t j = 0; j < 7; j++) { // 7 lines
+            uint8_t uc, ucMask = (1 << j);
+            for (uint8_t k=0; k<size_y; k++) { // repeat size_y lines
+                for (uint8_t i=0; i<5; i++) { // 5 columns
+                    uc = pgm_read_byte(&font[(c * 5) + i]);
+                    writeColor((uc & ucMask) ? color:bg, size_x);
+                } // for each column
+            } // repeat for each line of size_y
+        } // for j
+      } else { // slower text which doesn't overwrite the background color
+        for (int8_t i = 0; i < 5; i++) { // Char bitmap = 5 columns
+          uint8_t line = pgm_read_byte(&font[c * 5 + i]);
+          for (int8_t j = 0; j < 8; j++, line >>= 1) {
+            if (line & 1) {
+              if (size_x == 1 && size_y == 1)
+                writePixel(x + i, y + j, color);
+              else
+                writeFillRect(x + i * size_x, y + j * size_y, size_x, size_y,
                           color);
-        } else if (bg != color) {
+            } else if (bg != color) {
+              if (size_x == 1 && size_y == 1)
+                writePixel(x + i, y + j, bg);
+              else
+                writeFillRect(x + i * size_x, y + j * size_y, size_x, size_y, bg);
+            }
+          }
+        }
+        if (bg != color) { // If opaque, draw vertical line for last column
           if (size_x == 1 && size_y == 1)
-            writePixel(x + i, y + j, bg);
+            writeFastVLine(x + 5, y, 8, bg);
           else
-            writeFillRect(x + i * size_x, y + j * size_y, size_x, size_y, bg);
+            writeFillRect(x + 5 * size_x, y, size_x, 8 * size_y, bg);
         }
-      }
-    }
-    if (bg != color) { // If opaque, draw vertical line for last column
-      if (size_x == 1 && size_y == 1)
-        writeFastVLine(x + 5, y, 8, bg);
-      else
-        writeFillRect(x + 5 * size_x, y, size_x, 8 * size_y, bg);
     }
     endWrite();
 

Adafruit_GFX.h

@@ -32,6 +32,10 @@ class Adafruit_GFX : public Print {
   // These MAY be overridden by the subclass to provide device-specific
   // optimized code.  Otherwise 'generic' versions are used.
   virtual void startWrite(void);
+  virtual void setAddrWindow(uint16_t x, uint16_t y, uint16_t w, uint16_t h);
+  virtual void writeColor(uint16_t color, uint32_t len);
+  virtual void writePixels(uint16_t *colors, uint32_t len, bool block,
+                   bool bigEndian);
   virtual void writePixel(int16_t x, int16_t y, uint16_t color);
   virtual void writeFillRect(int16_t x, int16_t y, int16_t w, int16_t h,
                              uint16_t color);