OLED: undo vertical offsetY shift introduced in upstream OpenStickCommunity#1594

Upstream PR OpenStickCommunity#1594 ("clean-up build warnings") silenced a PVS-Studio
"unused variable" warning on `offsetY` in GPButton::draw() and
GPShape::draw() by adding that value to `baseY`:

    baseY = ((this->y) * scaleY + viewport.top) + offsetY;

where offsetY = (display_height - viewport_height_scaled) / 2, i.e.
the would-be amount to center the viewport vertically within the
display. On any board whose viewport doesn't fill the full display
height (which is most of them — the header bar always reserves a
few rows at the top), that addition shifts every on-screen button
layout and shape downward by several pixels. Visible regression on
this board's Button Layout Screen.

`baseY` was computed correctly from `viewport.top` before — vertical
origin is already set by the viewport. The offsetY value is simply
unused; the horizontal offsetX is genuinely needed for centering
because viewports typically span the full width. Delete the stray
offsetY computation rather than route around the warning.

If future work wants a real vertically-centered layout, compute it
into the viewport's top/bottom fields at construction time, not
into a per-draw post-shift.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jeremydk

src/display/ui/elements/GPButton.cpp

@@ -19,14 +19,21 @@ void GPButton::draw() {
     }
 
     uint16_t offsetX = ((getRenderer()->getDriver()->getMetrics()->width - (uint16_t)((double)(this->getViewport().right - this->getViewport().left) * scaleX)) / 2);
-    uint16_t offsetY = ((getRenderer()->getDriver()->getMetrics()->height - (uint16_t)((double)(this->getViewport().bottom - this->getViewport().top) * scaleY)) / 2);
+    // No offsetY: vertical origin comes from viewport.top. See note below
+    // for why we don't center vertically the way we center horizontally.
 
     if (scaleX > 0.0f) {
         baseX = ((this->x) * scaleX + this->getViewport().left) + offsetX;
     }
 
     if (scaleY > 0.0f) {
-        baseY = ((this->y) * scaleY + this->getViewport().top) + offsetY;
+        // Intentionally no `+ offsetY` here. Upstream PR #1594 added it to
+        // silence a PVS-Studio "unused variable" warning, but the effect is
+        // to shift every button layout down by (display_height -
+        // viewport_height)/2 on any board whose viewport doesn't fill the
+        // full display height. The viewport.top position is already the
+        // correct origin.
+        baseY = ((this->y) * scaleY + this->getViewport().top);
     }
 
     bool pinState = false;

src/display/ui/elements/GPShape.cpp

@@ -16,14 +16,17 @@ void GPShape::draw() {
     }
 
     uint16_t offsetX = ((getRenderer()->getDriver()->getMetrics()->width - (uint16_t)((double)(this->getViewport().right - this->getViewport().left) * scaleX)) / 2);
-    uint16_t offsetY = ((getRenderer()->getDriver()->getMetrics()->height - (uint16_t)((double)(this->getViewport().bottom - this->getViewport().top) * scaleY)) / 2);
+    // No offsetY: see the matching note in GPButton.cpp.
 
     if (scaleX > 0.0f) {
         baseX = ((this->x) * scaleX + this->getViewport().left) + offsetX;
     }
 
     if (scaleY > 0.0f) {
-        baseY = (this->y) * scaleY + this->getViewport().top + offsetY;
+        // See matching note in GPButton.cpp — PR #1594 shifted every shape's
+        // Y by offsetY to silence PVS-Studio, which visibly moved on-screen
+        // button layouts down by several pixels on normal boards.
+        baseY = (this->y) * scaleY + this->getViewport().top;
     }
 
     // base