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Perf/UI allocation reduction #1978

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c2aae65
perf: reuse ST7789 scanline buffer
robekl Mar 9, 2026
5e11362
perf: avoid heap allocation in OLED drawString
robekl Mar 9, 2026
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33 changes: 22 additions & 11 deletions src/helpers/ui/OLEDDisplay.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -619,11 +619,8 @@ uint16_t OLEDDisplay::drawStringInternal(int16_t xMove, int16_t yMove, const cha

uint16_t OLEDDisplay::drawString(int16_t xMove, int16_t yMove, const String &strUser) {
uint16_t lineHeight = pgm_read_byte(fontData + HEIGHT_POS);

// char* text must be freed!
char* text = strdup(strUser.c_str());
if (!text) {
DEBUG_OLEDDISPLAY("[OLEDDISPLAY][drawString] Can't allocate char array.\n");
const char* text = strUser.c_str();
if (text == nullptr) {
return 0;
}

Expand All @@ -642,13 +639,27 @@ uint16_t OLEDDisplay::drawString(int16_t xMove, int16_t yMove, const String &str

uint16_t charDrawn = 0;
uint16_t line = 0;
char* textPart = strtok(text,"\n");
while (textPart != NULL) {
uint16_t length = strlen(textPart);
charDrawn += drawStringInternal(xMove, yMove - yOffset + (line++) * lineHeight, textPart, length, getStringWidth(textPart, length, true), true);
textPart = strtok(NULL, "\n");
const char* lineStart = text;
while (true) {
const char* lineEnd = lineStart;
while (*lineEnd != 0 && *lineEnd != '\n') {
lineEnd++;
}

if (lineEnd == lineStart && *lineEnd == '\n') {
lineStart = lineEnd + 1;
continue;
}

uint16_t length = lineEnd - lineStart;
charDrawn += drawStringInternal(xMove, yMove - yOffset + (line++) * lineHeight, lineStart, length,
getStringWidth(lineStart, length, true), true);

if (*lineEnd == 0) {
break;
}
lineStart = lineEnd + 1;
}
free(text);
return charDrawn;
}

Expand Down
92 changes: 55 additions & 37 deletions src/helpers/ui/ST7789Spi.h
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Original file line number Diff line number Diff line change
Expand Up @@ -103,9 +103,11 @@ class ST7789Spi : public OLEDDisplay {
int _mosi;
int _clk;
SPIClass * _spi;
SPISettings _spiSettings;
SPISettings _spiSettings;
uint16_t _RGB=0xFFFF;
uint8_t _buffheight;
uint16_t* _pixbuf = nullptr;
uint32_t _pixbuf_capacity = 0;
public:
/* pass _cs as -1 to indicate "do not use CS pin", for cases where it is hard wired low */
ST7789Spi(SPIClass *spiClass,uint8_t _rst, uint8_t _dc, uint8_t _cs, OLEDDISPLAY_GEOMETRY g = GEOMETRY_RAWMODE,uint16_t width=240,uint16_t height=135,int mosi=-1,int miso=-1,int clk=-1) {
Expand All @@ -121,9 +123,29 @@ class ST7789Spi : public OLEDDisplay {
setGeometry(g,width,height);
}

~ST7789Spi() {
if (_pixbuf != nullptr) {
rtos_free(_pixbuf);
_pixbuf = nullptr;
_pixbuf_capacity = 0;
}
}

bool connect(){
this->_buffheight=displayHeight / 8;
this->_buffheight+=displayHeight % 8 ? 1:0;
if (_pixbuf == nullptr || _pixbuf_capacity < displayWidth) {
uint16_t* new_pixbuf = (uint16_t *)rtos_malloc(sizeof(uint16_t) * displayWidth);
if (new_pixbuf == nullptr) {
_pixbuf_capacity = 0;
return false;
}
if (_pixbuf != nullptr) {
rtos_free(_pixbuf);
}
_pixbuf = new_pixbuf;
_pixbuf_capacity = displayWidth;
}
pinMode(_cs, OUTPUT);
pinMode(_dc, OUTPUT);
//pinMode(_ledA, OUTPUT);
Expand Down Expand Up @@ -186,55 +208,51 @@ class ST7789Spi : public OLEDDisplay {
set_CS(LOW);
_spi->beginTransaction(_spiSettings);

for (y = minBoundY; y <= maxBoundY; y++)
{
for(int temp = 0; temp<8;temp++)
{
//setAddrWindow(minBoundX,y*8+temp,maxBoundX-minBoundX+1,1);
setAddrWindow(minBoundX,y*8+temp,maxBoundX-minBoundX+1,1);
//setAddrWindow(y*8+temp,minBoundX,1,maxBoundX-minBoundX+1);
uint32_t const pixbufcount = maxBoundX-minBoundX+1;
uint16_t *pixbuf = (uint16_t *)rtos_malloc(2 * pixbufcount);
for (x = minBoundX; x <= maxBoundX; x++)
{
pixbuf[x-minBoundX] = ((buffer[x + y * displayWidth]>>temp)&0x01)==1?_RGB:0;
}
for (y = minBoundY; y <= maxBoundY; y++)
{
for(int temp = 0; temp<8;temp++)
{
//setAddrWindow(minBoundX,y*8+temp,maxBoundX-minBoundX+1,1);
setAddrWindow(minBoundX,y*8+temp,maxBoundX-minBoundX+1,1);
//setAddrWindow(y*8+temp,minBoundX,1,maxBoundX-minBoundX+1);
uint32_t const pixbufcount = maxBoundX-minBoundX+1;
for (x = minBoundX; x <= maxBoundX; x++)
{
_pixbuf[x-minBoundX] = ((buffer[x + y * displayWidth]>>temp)&0x01)==1?_RGB:0;
}
#ifdef ESP_PLATFORM
_spi->transferBytes((uint8_t *)pixbuf, NULL, 2 * pixbufcount);
_spi->transferBytes((uint8_t *)_pixbuf, NULL, 2 * pixbufcount);
#else
_spi->transfer(pixbuf, NULL, 2 * pixbufcount);
_spi->transfer(_pixbuf, NULL, 2 * pixbufcount);
#endif
rtos_free(pixbuf);
}
}
}
}
_spi->endTransaction();
set_CS(HIGH);

#else
set_CS(LOW);
_spi->beginTransaction(_spiSettings);
uint8_t x, y;
for (y = 0; y < _buffheight; y++)
{
for(int temp = 0; temp<8;temp++)
{
//setAddrWindow(minBoundX,y*8+temp,maxBoundX-minBoundX+1,1);
//setAddrWindow(minBoundX,y*8+temp,maxBoundX-minBoundX+1,1);
setAddrWindow(y*8+temp,0,1,displayWidth);
uint32_t const pixbufcount = displayWidth;
uint16_t *pixbuf = (uint16_t *)rtos_malloc(2 * pixbufcount);
for (x = 0; x < displayWidth; x++)
{
pixbuf[x] = ((buffer[x + y * displayWidth]>>temp)&0x01)==1?_RGB:0;
}
for (y = 0; y < _buffheight; y++)
{
for(int temp = 0; temp<8;temp++)
{
//setAddrWindow(minBoundX,y*8+temp,maxBoundX-minBoundX+1,1);
//setAddrWindow(minBoundX,y*8+temp,maxBoundX-minBoundX+1,1);
setAddrWindow(y*8+temp,0,1,displayWidth);
uint32_t const pixbufcount = displayWidth;
for (x = 0; x < displayWidth; x++)
{
_pixbuf[x] = ((buffer[x + y * displayWidth]>>temp)&0x01)==1?_RGB:0;
}
#ifdef ESP_PLATFORM
_spi->transferBytes((uint8_t *)pixbuf, NULL, 2 * pixbufcount);
_spi->transferBytes((uint8_t *)_pixbuf, NULL, 2 * pixbufcount);
#else
_spi->transfer(pixbuf, NULL, 2 * pixbufcount);
_spi->transfer(_pixbuf, NULL, 2 * pixbufcount);
#endif
rtos_free(pixbuf);
}
}
}
}
_spi->endTransaction();
set_CS(HIGH);

Expand Down