Use negative z postion for sixel and iterm2 protocol images

remove all characters covered by the image before placing the image.

src/Screen.cpp

@@ -242,6 +242,15 @@ void Screen::eraseChars(int n)
     clearImage(loc(_cuX, _cuY), loc(p, _cuY), ' ', false);
 }
 
+void Screen::eraseBlock(int y, int x, int height, int width)
+{
+    width = qBound(0, width, _columns - x - 1);
+    height = qBound(0, height, _lines - y - 1);
+    for (int row = y; row < y + height; row++) {
+        clearImage(loc(x, row), loc(x + width - 1, row), ' ', false);
+    }
+}
+
 void Screen::deleteChars(int n)
 {
     Q_ASSERT(n >= 0);
@@ -1808,6 +1817,7 @@ int Screen::addPlacement(QPixmap pixmap,
                          int col,
                          bool scrolling,
                          bool moveCursor,
+                         bool leaveText,
                          int z,
                          int id,
                          int pid,
@@ -1847,6 +1857,9 @@ int Screen::addPlacement(QPixmap pixmap,
     p->X = X;
     p->Y = Y;
 
+    if (!leaveText) {
+        eraseBlock(row, col, rows, cols);
+    }
     addPlacement(p);
     int needScroll = qBound(0, row + rows - _lines + 1, rows);
     if (moveCursor && scrolling && needScroll > moveCursor) {

src/Screen.h

@@ -619,7 +619,8 @@ public:
                      int col = -1,
                      bool scrolling = true,
                      bool moveCursor = true,
-                     int z = 1,
+                     bool leaveText = false,
+                     int z = -1000,
                      int id = -1,
                      int pid = -1,
                      qreal opacity = 1.0,
@@ -661,6 +662,9 @@ private:
     // if resetLineRendition is true, all completely cleared lines will be set to single-width.
     void clearImage(int loca, int loce, char c, bool resetLineRendition = true);
 
+    // erases a rectangular section of the screen.
+    void eraseBlock(int y, int x, int height, int width);
+
     // move screen image between 'sourceBegin' and 'sourceEnd' to 'dest'.
     // the parameters are specified as offsets from the start of the screen image.
     // the loc(x,y) macro can be used to generate these values from a column,line pair.

src/Vt102Emulation.cpp

@@ -1464,8 +1464,20 @@ void Vt102Emulation::processGraphicsToken(int tokenSize)
                                        keys['r'] * _currentScreen->currentTerminalDisplay()->terminalFont()->fontHeight());
             }
             int rows = -1, cols = -1;
-            _currentScreen
-                ->addPlacement(pixmap, rows, cols, -1, -1, true, keys['C'] == 0, keys['z'], keys['i'], keys['p'], keys['A'] / 255.0, keys['X'], keys['Y']);
+            _currentScreen->addPlacement(pixmap,
+                                         rows,
+                                         cols,
+                                         -1,
+                                         -1,
+                                         true,
+                                         keys['C'] == 0,
+                                         true,
+                                         keys['z'],
+                                         keys['i'],
+                                         keys['p'],
+                                         keys['A'] / 255.0,
+                                         keys['X'],
+                                         keys['Y']);
             if (keys['q'] == 0 && keys['i']) {
                 QString params = QStringLiteral("i=") + QString::number(keys['i']);
                 if (keys['I']) {
@@ -2230,7 +2242,7 @@ void Vt102Emulation::SixelModeDisable()
         pixmap = pixmap.scaled(pixmap.width(), m_aspect.first * pixmap.height() / m_aspect.second);
     }
     int rows = -1, cols = -1;
-    int needScroll = _currentScreen->addPlacement(pixmap, rows, cols, row, col, m_SixelScrolling, false);
+    int needScroll = _currentScreen->addPlacement(pixmap, rows, cols, row, col, m_SixelScrolling, false, false);
     if (m_SixelScrolling) {
         if (rows - needScroll > 0) {
             _currentScreen->cursorDown(rows - needScroll);