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Harden graphical scrollbar rendering #415

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Merged
forntoh merged 1 commit into from
May 19, 2026
Merged

Harden graphical scrollbar rendering #415

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21 changes: 14 additions & 7 deletions src/renderer/GraphicalDisplayRenderer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -402,19 +402,26 @@ void GraphicalDisplayRenderer::drawScrollBar() {
return;
}

uint8_t x = gDisplay->getDisplayWidth() - scrollbarWidth;
uint8_t areaHeight = rows * rowHeight();
if (areaHeight > gDisplay->getDisplayHeight()) {
areaHeight = gDisplay->getDisplayHeight();
uint8_t displayWidth = gDisplay->getDisplayWidth();
uint16_t areaHeight16 = static_cast<uint16_t>(rows) * rowHeight();
if (areaHeight16 > gDisplay->getDisplayHeight()) {
areaHeight16 = gDisplay->getDisplayHeight();
}
uint8_t areaHeight = static_cast<uint8_t>(areaHeight16);

uint8_t x = displayWidth - scrollbarWidth;

gDisplay->setDrawColor(0);
gDisplay->drawBox(x, 0, scrollbarWidth, areaHeight);
gDisplay->setDrawColor(1);

uint8_t handleHeight = (static_cast<uint16_t>(rows) * areaHeight) / totalItems;
if (handleHeight < 2) {
handleHeight = 2;
}

uint16_t scrollRange = totalItems - rows;
uint16_t trackRange = areaHeight - handleHeight;
uint8_t y = scrollRange == 0 ? 0 : (static_cast<uint16_t>(viewStart) * trackRange) / scrollRange;
uint16_t trackRange = areaHeight > handleHeight ? areaHeight - handleHeight : 0;
uint16_t scrollRange = totalItems > rows ? totalItems - rows : 1;
uint8_t y = (static_cast<uint16_t>(viewStart) * trackRange) / scrollRange;
gDisplay->drawBox(x, y, scrollbarWidth, handleHeight);
}
19 changes: 18 additions & 1 deletion test/GraphicalDisplayRenderer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ class StubGraphicalDisplay : public GraphicalDisplayInterface {
uint8_t drawColorCount = 0;
uint8_t drawColors[4] = {0, 0, 0, 0};
uint8_t lastDrawBoxHeight = 0;
uint8_t lastDrawBoxY = 0;

void begin() override {}
void clear() override {}
Expand Down Expand Up @@ -43,8 +44,9 @@ class StubGraphicalDisplay : public GraphicalDisplayInterface {
}
void clearBuffer() override {}
void sendBuffer() override {}
void drawBox(uint8_t, uint8_t, uint8_t, uint8_t h) override {
void drawBox(uint8_t, uint8_t y, uint8_t, uint8_t h) override {
drawBoxCount++;
lastDrawBoxY = y;
lastDrawBoxHeight = h;
}
void drawFrame(uint8_t, uint8_t, uint8_t, uint8_t) override {}
Expand Down Expand Up @@ -84,6 +86,21 @@ unittest(graphical_renderer_uses_tight_row_height) {
assertEqual(8, display.lastDrawBoxHeight);
}

unittest(graphical_renderer_clears_scrollbar_track_before_handle) {
StubGraphicalDisplay display;
GraphicalDisplayRenderer renderer(&display);

renderer.setViewportContext(0, 9);
renderer.drawItem("Label", NULL);

assertEqual(3, display.drawBoxCount);
assertEqual(0, display.drawColors[0]);
assertEqual(1, display.drawColors[1]);
assertEqual(0, display.drawColors[2]);
assertEqual(1, display.drawColors[3]);
assertEqual(0, display.lastDrawBoxY);
}

unittest(graphical_renderer_colors_indicators_when_focused) {
StubGraphicalDisplay display;
FocusableGraphicalDisplayRenderer renderer(&display);
Expand Down
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