update transparent window backgrounds on bg change

ChangeLog

@@ -1,6 +1,9 @@
 (Format: Year/Month/Day)
 Changes for 0.9.16:
 *06/04/21:
+   * Update all transparent things when bg changes (Simon)
+     (fixes sf.net #1446516 - slit transparency on start)
+     FbTk/... FbPixmap.cc FbWindow.hh/cc
    * Make border between tabs same width/color as window border (Simon)
      (sf.net #1473870)
      FbWinFrame.cc

src/FbTk/FbPixmap.cc

@@ -25,6 +25,7 @@
 #include "App.hh"
 #include "GContext.hh"
 #include "Transparent.hh"
+#include "FbWindow.hh"
 
 #include <X11/Xutil.h>
 #include <X11/Xatom.h>
@@ -390,9 +391,14 @@ void FbPixmap::rootwinPropertyNotify(int screen_num, Atom atom) {
 void FbPixmap::setRootPixmap(int screen_num, Pixmap pm) {
     if (!m_root_pixmaps) {
         m_root_pixmaps = new Pixmap[ScreenCount(display())];
+        for (int i=0; i < ScreenCount(display()); ++i)
+            m_root_pixmaps[i] = None;
     }
 
-    m_root_pixmaps[screen_num] = pm;
+    if (m_root_pixmaps[screen_num] != pm) {
+        m_root_pixmaps[screen_num] = pm;
+        FbWindow::updatedAlphaBackground(screen_num);
+    }
 }
 
 Pixmap FbPixmap::getRootPixmap(int screen_num, bool force_update) {

src/FbTk/FbWindow.cc

@@ -118,8 +118,10 @@ FbWindow::FbWindow(Window client):FbDrawable(), m_parent(0),
 FbWindow::~FbWindow() {
 
     // Need to free xrender pics before destroying window
-    if (m_transparent.get() != 0)
+    if (m_transparent.get() != 0) {
+        removeAlphaWin(*this);
         m_transparent.reset(0);
+    }
 
     if (m_window != 0) {
         // so we don't get any dangling eventhandler for this window
@@ -127,6 +129,7 @@ FbWindow::~FbWindow() {
         if (m_destroy)
             XDestroyWindow(display(), m_window);
     }
+
 }
 
 void FbWindow::setBackgroundColor(const FbTk::Color &bg_color) {
@@ -319,8 +322,10 @@ void FbWindow::updateTransparent(int the_x, int the_y, unsigned int the_width, u
 void FbWindow::setAlpha(unsigned char alpha) {
 #ifdef HAVE_XRENDER
     if (FbTk::Transparent::haveComposite()) {
-        if (m_transparent.get() != 0)
+        if (m_transparent.get() != 0) {
+            removeAlphaWin(*this);
             m_transparent.reset(0);
+        }
 
         // don't setOpaque, let controlling objects do that
         // since it's only needed on toplevel windows
@@ -330,10 +335,13 @@ void FbWindow::setAlpha(unsigned char alpha) {
 
         if (m_transparent.get() == 0 && alpha < 255) {
             m_transparent.reset(new Transparent(FbPixmap::getRootPixmap(screenNumber()), window(), alpha, screenNumber()));
+            addAlphaWin(*this);
         } else if (alpha < 255 && alpha != m_transparent->alpha())
             m_transparent->setAlpha(alpha);
-        else if (alpha == 255)
+        else if (alpha == 255) {
+            removeAlphaWin(*this);
             m_transparent.reset(0); // destroy transparent object
+        }
     }
 #endif // HAVE_XRENDER
 }
@@ -592,6 +600,29 @@ void FbWindow::sendConfigureNotify(int x, int y,
 
 }
 
+FbWindow::FbWinList FbWindow::m_alpha_wins;
+
+void FbWindow::addAlphaWin(FbWindow &win) {
+    m_alpha_wins.insert(&win);
+}
+
+void FbWindow::removeAlphaWin(FbWindow &win) {
+    FbWinList::iterator it = m_alpha_wins.find(&win);
+    if (it != m_alpha_wins.end())
+        m_alpha_wins.erase(it);
+}
+
+void FbWindow::updatedAlphaBackground(int screen) {
+    FbWinList::iterator it = m_alpha_wins.begin();
+    FbWinList::iterator it_end = m_alpha_wins.end();
+    for (; it != it_end; ++it) {
+        if ((*it)->screenNumber() == screen) {
+            (*it)->updateBackground(false);
+            (*it)->clear();
+        }
+    }
+}
+
 bool operator == (Window win, const FbWindow &fbwin) {
     return win == fbwin.window();
 }

src/FbTk/FbWindow.hh

@@ -29,6 +29,7 @@
 #include <X11/Xlib.h>
 #include <memory>
 #include <string>
+#include <set>
 
 namespace FbTk {
 
@@ -194,6 +195,8 @@ public:
     /// forces full background change, recalcing of alpha values if necessary
     void updateBackground(bool only_if_alpha);
 
+    static void updatedAlphaBackground(int screen);
+
 protected:
     /// creates a window with x window client (m_window = client)
     explicit FbWindow(Window client);
@@ -226,6 +229,12 @@ private:
     Pixmap m_lastbg_pm;
 
     FbWindowRenderer *m_renderer;
+
+    static void addAlphaWin(FbWindow &win);
+    static void removeAlphaWin(FbWindow &win);
+
+    typedef std::set<FbWindow *> FbWinList;
+    static FbWinList m_alpha_wins;
 };
 
 bool operator == (Window win, const FbWindow &fbwin);