28x terminal redraw improvement.

dvx/dvxApp.c

@@ -1338,9 +1338,20 @@ static void pollAnsiTermWidgetsWalk(AppContextT *ctx, WidgetT *w, WindowT *win)
     if (w->type == WidgetAnsiTermE) {
         wgtAnsiTermPoll(w);
 
-        if (wgtAnsiTermRepaint(w) > 0) {
+        int32_t dirtyY = 0;
+        int32_t dirtyH = 0;
+
+        if (wgtAnsiTermRepaint(w, &dirtyY, &dirtyH) > 0) {
             win->contentDirty = true;
-            dvxInvalidateWindow(ctx, win);
+
+            // Dirty only the affected rows (in screen coords) instead of
+            // the entire window. This dramatically reduces compositor and
+            // LFB flush work for cursor blink and single-row updates.
+            int32_t scrollY = win->vScroll ? win->vScroll->value : 0;
+            int32_t rectX   = win->x + win->contentX;
+            int32_t rectY   = win->y + win->contentY + dirtyY - scrollY;
+            int32_t rectW   = win->contentW;
+            dirtyListAdd(&ctx->dirty, rectX, rectY, rectW, dirtyH);
         }
     }
 

dvx/dvxDraw.c

@@ -432,6 +432,143 @@ void drawMaskedBitmap(DisplayT *d, const BlitOpsT *ops, int32_t x, int32_t y, in
 }
 
 
+// ============================================================
+// drawTermRow
+// ============================================================
+//
+// Renders an entire row of terminal character cells in one pass.
+// lineData points to (ch, attr) pairs.  palette is a 16-entry
+// packed-color table.  This avoids per-character function call
+// overhead, redundant clip calculation, and spanFill startup
+// costs that make drawChar expensive when called 80× per row.
+
+void drawTermRow(DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font, int32_t x, int32_t y, int32_t cols, const uint8_t *lineData, const uint32_t *palette, bool blinkVisible, int32_t cursorCol) {
+    int32_t cw    = font->charWidth;
+    int32_t ch    = font->charHeight;
+    int32_t bpp   = ops->bytesPerPixel;
+    int32_t pitch = d->pitch;
+
+    // Row-level clip: reject if entirely outside vertically
+    int32_t clipX1 = d->clipX;
+    int32_t clipX2 = d->clipX + d->clipW;
+    int32_t clipY1 = d->clipY;
+    int32_t clipY2 = d->clipY + d->clipH;
+
+    if (y + ch <= clipY1 || y >= clipY2) {
+        return;
+    }
+
+    // Vertical clip for glyph scanlines
+    int32_t rowStart = 0;
+    int32_t rowEnd   = ch;
+    if (y < clipY1) { rowStart = clipY1 - y; }
+    if (y + ch > clipY2) { rowEnd = clipY2 - y; }
+
+    // Horizontal clip: find first and last visible column
+    int32_t rowW     = cols * cw;
+    int32_t firstCol = 0;
+    int32_t lastCol  = cols;
+
+    if (x + rowW <= clipX1 || x >= clipX2) {
+        return;
+    }
+
+    if (x < clipX1) {
+        firstCol = (clipX1 - x) / cw;
+    }
+
+    if (x + rowW > clipX2) {
+        lastCol = (clipX2 - x + cw - 1) / cw;
+        if (lastCol > cols) { lastCol = cols; }
+    }
+
+    // Per-column clip for partially visible edge cells
+    int32_t edgeColStart = 0;
+
+    if (x + firstCol * cw < clipX1) {
+        edgeColStart = clipX1 - (x + firstCol * cw);
+    }
+
+    // Render each visible cell
+    for (int32_t col = firstCol; col < lastCol; col++) {
+        uint8_t  gch  = lineData[col * 2];
+        uint8_t  attr = lineData[col * 2 + 1];
+        uint32_t fg   = palette[attr & 0x0F];
+        uint32_t bg   = palette[(attr >> 4) & 0x07];
+
+        // Blink: hide text during off phase
+        if ((attr & 0x80) && !blinkVisible) {
+            fg = bg;
+        }
+
+        // Cursor: invert colors
+        if (col == cursorCol) {
+            uint32_t tmp = fg;
+            fg = bg;
+            bg = tmp;
+        }
+
+        int32_t cx = x + col * cw;
+
+        // Determine per-cell horizontal clip
+        int32_t cStart = 0;
+        int32_t cEnd   = cw;
+
+        if (col == firstCol) {
+            cStart = edgeColStart;
+        }
+
+        if (cx + cw > clipX2) {
+            cEnd = clipX2 - cx;
+        }
+
+        // Look up glyph data
+        int32_t idx = (uint8_t)gch - font->firstChar;
+        const uint8_t *glyph = NULL;
+
+        if (idx >= 0 && idx < font->numChars) {
+            glyph = font->glyphData + idx * ch;
+        }
+
+        // Render scanlines
+        if (bpp == 2) {
+            uint16_t fg16 = (uint16_t)fg;
+            uint16_t bg16 = (uint16_t)bg;
+
+            for (int32_t row = rowStart; row < rowEnd; row++) {
+                uint16_t *dst = (uint16_t *)(d->backBuf + (y + row) * pitch + cx * 2);
+                uint8_t   bits = glyph ? glyph[row] : 0;
+
+                for (int32_t p = cStart; p < cEnd; p++) {
+                    dst[p] = (bits & (0x80 >> p)) ? fg16 : bg16;
+                }
+            }
+        } else if (bpp == 4) {
+            for (int32_t row = rowStart; row < rowEnd; row++) {
+                uint32_t *dst = (uint32_t *)(d->backBuf + (y + row) * pitch + cx * 4);
+                uint8_t   bits = glyph ? glyph[row] : 0;
+
+                for (int32_t p = cStart; p < cEnd; p++) {
+                    dst[p] = (bits & (0x80 >> p)) ? fg : bg;
+                }
+            }
+        } else {
+            uint8_t fg8 = (uint8_t)fg;
+            uint8_t bg8 = (uint8_t)bg;
+
+            for (int32_t row = rowStart; row < rowEnd; row++) {
+                uint8_t *dst = d->backBuf + (y + row) * pitch + cx;
+                uint8_t  bits = glyph ? glyph[row] : 0;
+
+                for (int32_t p = cStart; p < cEnd; p++) {
+                    dst[p] = (bits & (0x80 >> p)) ? fg8 : bg8;
+                }
+            }
+        }
+    }
+}
+
+
 // ============================================================
 // drawText
 // ============================================================

dvx/dvxDraw.h

@@ -39,6 +39,11 @@ int32_t textWidthAccel(const BitmapFontT *font, const char *text);
 // andMask/xorData are arrays of uint16_t, one per row
 void drawMaskedBitmap(DisplayT *d, const BlitOpsT *ops, int32_t x, int32_t y, int32_t w, int32_t h, const uint16_t *andMask, const uint16_t *xorData, uint32_t fgColor, uint32_t bgColor);
 
+// Draw a row of terminal character cells (ch/attr pairs with a 16-color palette).
+// Renders 'cols' cells starting at (x,y). Much faster than calling drawChar per cell.
+// cursorCol: column index to draw inverted (cursor), or -1 for no cursor.
+void drawTermRow(DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font, int32_t x, int32_t y, int32_t cols, const uint8_t *lineData, const uint32_t *palette, bool blinkVisible, int32_t cursorCol);
+
 // Dotted focus rectangle (every other pixel)
 void drawFocusRect(DisplayT *d, const BlitOpsT *ops, int32_t x, int32_t y, int32_t w, int32_t h, uint32_t color);
 

dvx/dvxWidget.h

@@ -327,6 +327,9 @@ typedef struct WidgetT {
             uint32_t dirtyRows;       // bitmask of rows needing repaint
             int32_t  lastCursorRow;   // cursor row at last repaint
             int32_t  lastCursorCol;   // cursor col at last repaint
+            // Cached packed palette (avoids packColor per repaint)
+            uint32_t packedPalette[16];
+            bool     paletteValid;
             // Communications interface (all NULL = disconnected)
             void    *commCtx;
             int32_t (*commRead)(void *ctx, uint8_t *buf, int32_t maxLen);
@@ -519,8 +522,9 @@ int32_t wgtAnsiTermPoll(WidgetT *w);
 
 // Fast repaint: renders only dirty rows directly into the window's content
 // buffer, bypassing the full widget paint pipeline. Returns number of rows
-// repainted (0 if nothing was dirty).
+// repainted (0 if nothing was dirty). If outY/outH are non-NULL, they receive
-int32_t wgtAnsiTermRepaint(WidgetT *w);
+// the content-buffer-relative Y and height of the repainted region.
+int32_t wgtAnsiTermRepaint(WidgetT *w, int32_t *outY, int32_t *outH);
 
 // ============================================================
 // Operations

dvx/widgets/widgetAnsiTerm.c

@@ -60,6 +60,7 @@ static const int32_t sAnsiToCga[8] = { 0, 4, 2, 6, 1, 5, 3, 7 };
 // ============================================================
 
 static void ansiTermAddToScrollback(WidgetT *w, int32_t screenRow);
+static void ansiTermBuildPalette(WidgetT *w, const DisplayT *d);
 static void ansiTermDeleteLines(WidgetT *w, int32_t count);
 static void ansiTermDirtyRange(WidgetT *w, int32_t startCell, int32_t count);
 static void ansiTermDirtyRow(WidgetT *w, int32_t row);
@@ -104,6 +105,27 @@ static void ansiTermAddToScrollback(WidgetT *w, int32_t screenRow) {
 }
 
 
+// ============================================================
+// ansiTermBuildPalette
+// ============================================================
+//
+// Build the packed 16-color palette and cache it in the widget.
+// Only recomputed when paletteValid is false (first use or
+// after a display format change).
+
+static void ansiTermBuildPalette(WidgetT *w, const DisplayT *d) {
+    if (w->as.ansiTerm.paletteValid) {
+        return;
+    }
+
+    for (int32_t i = 0; i < 16; i++) {
+        w->as.ansiTerm.packedPalette[i] = packColor(d, sCgaPalette[i][0], sCgaPalette[i][1], sCgaPalette[i][2]);
+    }
+
+    w->as.ansiTerm.paletteValid = true;
+}
+
+
 // ============================================================
 // ansiTermDirtyRange
 // ============================================================
@@ -1164,7 +1186,7 @@ int32_t wgtAnsiTermPoll(WidgetT *w) {
 // no relayout, no other widgets). This keeps ACK turnaround fast
 // for the serial link.
 
-int32_t wgtAnsiTermRepaint(WidgetT *w) {
+int32_t wgtAnsiTermRepaint(WidgetT *w, int32_t *outY, int32_t *outH) {
     if (!w || w->type != WidgetAnsiTermE || !w->window) {
         return 0;
     }
@@ -1216,19 +1238,18 @@ int32_t wgtAnsiTermRepaint(WidgetT *w) {
 
     int32_t cols  = w->as.ansiTerm.cols;
     int32_t rows  = w->as.ansiTerm.rows;
-    int32_t cellW = font->charWidth;
     int32_t cellH = font->charHeight;
     int32_t baseX = w->x + ANSI_BORDER;
     int32_t baseY = w->y + ANSI_BORDER;
 
-    // Build palette
+    // Use cached palette
-    uint32_t palette[16];
+    ansiTermBuildPalette(w, &cd);
-    for (int32_t i = 0; i < 16; i++) {
+    const uint32_t *palette = w->as.ansiTerm.packedPalette;
-        palette[i] = packColor(&cd, sCgaPalette[i][0], sCgaPalette[i][1], sCgaPalette[i][2]);
-    }
 
-    bool viewingLive = (w->as.ansiTerm.scrollPos == w->as.ansiTerm.scrollbackCount);
+    bool    viewingLive = (w->as.ansiTerm.scrollPos == w->as.ansiTerm.scrollbackCount);
-    int32_t repainted = 0;
+    int32_t repainted   = 0;
+    int32_t minRow      = rows;
+    int32_t maxRow      = -1;
 
     for (int32_t row = 0; row < rows; row++) {
         if (!(dirty & (1U << row))) {
@@ -1238,37 +1259,27 @@ int32_t wgtAnsiTermRepaint(WidgetT *w) {
         int32_t lineIndex = w->as.ansiTerm.scrollPos + row;
         const uint8_t *lineData = ansiTermGetLine(w, lineIndex);
 
-        for (int32_t col = 0; col < cols; col++) {
+        // Cursor column for this row (-1 if cursor not on this row)
-            uint8_t ch   = lineData[col * 2];
+        int32_t curCol2 = -1;
-            uint8_t attr = lineData[col * 2 + 1];
+        if (viewingLive && w->as.ansiTerm.cursorVisible && w->as.ansiTerm.cursorOn &&
-
+            row == w->as.ansiTerm.cursorRow) {
-            uint32_t fg = palette[attr & ATTR_FG_MASK];
+            curCol2 = w->as.ansiTerm.cursorCol;
-            uint32_t bg = palette[(attr >> 4) & 0x07];
-
-            // Blink: hide text during off phase
-            if ((attr & ATTR_BLINK_BIT) && !w->as.ansiTerm.blinkVisible) {
-                fg = bg;
-            }
-
-            if (viewingLive && w->as.ansiTerm.cursorVisible && w->as.ansiTerm.cursorOn &&
-                row == w->as.ansiTerm.cursorRow && col == w->as.ansiTerm.cursorCol) {
-                uint32_t tmp = fg;
-                fg = bg;
-                bg = tmp;
-            }
-
-            int32_t cx = baseX + col * cellW;
-            int32_t cy = baseY + row * cellH;
-
-            drawChar(&cd, ops, font, cx, cy, (char)ch, fg, bg, true);
         }
 
+        drawTermRow(&cd, ops, font, baseX, baseY + row * cellH, cols, lineData, palette, w->as.ansiTerm.blinkVisible, curCol2);
+
+        if (row < minRow) { minRow = row; }
+        if (row > maxRow) { maxRow = row; }
         repainted++;
     }
 
     w->as.ansiTerm.dirtyRows      = 0;
     w->as.ansiTerm.lastCursorRow  = w->as.ansiTerm.cursorRow;
     w->as.ansiTerm.lastCursorCol  = w->as.ansiTerm.cursorCol;
+
+    if (outY) { *outY = baseY + minRow * cellH; }
+    if (outH) { *outH = (maxRow - minRow + 1) * cellH; }
+
     return repainted;
 }
 
@@ -1497,12 +1508,9 @@ void widgetAnsiTermPaint(WidgetT *w, DisplayT *d, const BlitOpsT *ops, const Bit
     bevel.width     = ANSI_BORDER;
     drawBevel(d, ops, w->x, w->y, w->w, w->h, &bevel);
 
-    // Build the 16-color packed palette for this display format
+    // Build/cache the 16-color packed palette
-    uint32_t palette[16];
+    ansiTermBuildPalette(w, d);
-
+    const uint32_t *palette = w->as.ansiTerm.packedPalette;
-    for (int32_t i = 0; i < 16; i++) {
-        palette[i] = packColor(d, sCgaPalette[i][0], sCgaPalette[i][1], sCgaPalette[i][2]);
-    }
 
     int32_t  cols    = w->as.ansiTerm.cols;
     int32_t  rows    = w->as.ansiTerm.rows;
@@ -1515,36 +1523,19 @@ void widgetAnsiTermPaint(WidgetT *w, DisplayT *d, const BlitOpsT *ops, const Bit
     // Determine if viewing live terminal or scrollback
     bool viewingLive = (w->as.ansiTerm.scrollPos == sbCount);
 
-    // Render character cells
+    // Render character cells row by row using bulk renderer
     for (int32_t row = 0; row < rows; row++) {
         int32_t lineIndex = w->as.ansiTerm.scrollPos + row;
         const uint8_t *lineData = ansiTermGetLine(w, lineIndex);
 
-        for (int32_t col = 0; col < cols; col++) {
+        // Cursor column for this row (-1 if cursor not on this row)
-            uint8_t ch   = lineData[col * 2];
+        int32_t curCol = -1;
-            uint8_t attr = lineData[col * 2 + 1];
+        if (viewingLive && w->as.ansiTerm.cursorVisible && w->as.ansiTerm.cursorOn &&
-
+            row == w->as.ansiTerm.cursorRow) {
-            uint32_t fg = palette[attr & ATTR_FG_MASK];
+            curCol = w->as.ansiTerm.cursorCol;
-            uint32_t bg = palette[(attr >> 4) & 0x07];
-
-            // Blink: hide text during off phase
-            if ((attr & ATTR_BLINK_BIT) && !w->as.ansiTerm.blinkVisible) {
-                fg = bg;
-            }
-
-            // Draw cursor as inverse block (only when viewing live terminal)
-            if (viewingLive && w->as.ansiTerm.cursorVisible && w->as.ansiTerm.cursorOn &&
-                row == w->as.ansiTerm.cursorRow && col == w->as.ansiTerm.cursorCol) {
-                uint32_t tmp = fg;
-                fg = bg;
-                bg = tmp;
-            }
-
-            int32_t cx = baseX + col * cellW;
-            int32_t cy = baseY + row * cellH;
-
-            drawChar(d, ops, font, cx, cy, (char)ch, fg, bg, true);
         }
+
+        drawTermRow(d, ops, font, baseX, baseY + row * cellH, cols, lineData, palette, w->as.ansiTerm.blinkVisible, curCol);
     }
 
     // Draw scrollbar