Refactor GUI rendering model to be two-phased.

Instead of clients painting whenever they feel like it, we now ask that they
paint in response to a paint message.

After finishing painting, clients notify the WindowServer about the rect(s)
they painted into and then flush eventually happens, etc.

This stuff leaves us with a lot of badly named things. Need to fix that.

Kernel/Process.h

@@ -201,6 +201,7 @@ public:
     int gui$get_window_backing_store(int window_id, GUI_WindowBackingStoreInfo*);
     int gui$release_window_backing_store(void* backing_store_id);
     int gui$invalidate_window(int window_id, const GUI_Rect*);
+    int gui$notify_paint_finished(int window_id, const GUI_Rect*);
     int gui$get_window_title(int window_id, char* buffer, size_t size);
     int gui$set_window_title(int window_id, const char* title, size_t size);
     int gui$get_window_rect(int window_id, GUI_Rect*);

Kernel/ProcessGUI.cpp

@@ -126,28 +126,50 @@ int Process::gui$release_window_backing_store(void* backing_store_id)
     return -EBADBACKING;
 }
 
-int Process::gui$invalidate_window(int window_id, const GUI_Rect* rect)
+int Process::gui$invalidate_window(int window_id, const GUI_Rect* a_rect)
 {
     if (window_id < 0)
         return -EINVAL;
-    if (rect && !validate_read_typed(rect))
+    if (a_rect && !validate_read_typed(a_rect))
         return -EFAULT;
     auto it = m_windows.find(window_id);
     if (it == m_windows.end())
         return -EBADWINDOW;
 #ifdef LOG_GUI_SYSCALLS
-    if (!rect)
+    if (!a_rect)
         dbgprintf("%s<%u> gui$invalidate_window (window_id=%d, rect=(entire))\n", name().characters(), pid(), window_id);
     else
-        dbgprintf("%s<%u> gui$invalidate_window (window_id=%d, rect={%d,%d %dx%d})\n", name().characters(), pid(), window_id, rect->location.x, rect->location.y, rect->size.width, rect->size.height);
+        dbgprintf("%s<%u> gui$invalidate_window (window_id=%d, rect={%d,%d %dx%d})\n", name().characters(), pid(), window_id, a_rect->location.x, a_rect->location.y, a_rect->size.width, a_rect->size.height);
 #endif
     auto& window = *(*it).value;
-    Rect invalidation_rect;
-    if (rect) {
-        WSWindowLocker locker(window);
-        invalidation_rect = *rect;
-    }
-    WSEventLoop::the().post_event(&window, make<WSWindowInvalidationEvent>(invalidation_rect));
+    Rect rect;
+    if (a_rect)
+        rect = *a_rect;
+    WSEventLoop::the().post_event(&window, make<WSPaintEvent>(rect));
+    WSEventLoop::the().server_process().request_wakeup();
+    return 0;
+}
+
+int Process::gui$notify_paint_finished(int window_id, const GUI_Rect* a_rect)
+{
+    if (window_id < 0)
+        return -EINVAL;
+    if (a_rect && !validate_read_typed(a_rect))
+        return -EFAULT;
+    auto it = m_windows.find(window_id);
+    if (it == m_windows.end())
+        return -EBADWINDOW;
+#ifdef LOG_GUI_SYSCALLS
+    if (!a_rect)
+        dbgprintf("%s<%u> gui$notify_paint_finished (window_id=%d, rect=(entire))\n", name().characters(), pid(), window_id);
+    else
+        dbgprintf("%s<%u> gui$notify_paint_finished (window_id=%d, rect={%d,%d %dx%d})\n", name().characters(), pid(), window_id, a_rect->location.x, a_rect->location.y, a_rect->size.width, a_rect->size.height);
+#endif
+    auto& window = *(*it).value;
+    Rect rect;
+    if (a_rect)
+        rect = *a_rect;
+    WSEventLoop::the().post_event(&window, make<WSWindowInvalidationEvent>(rect));
     WSEventLoop::the().server_process().request_wakeup();
     return 0;
 }

Kernel/Syscall.cpp

@@ -215,6 +215,8 @@ static dword handle(RegisterDump& regs, dword function, dword arg1, dword arg2,
         return current->gui$get_window_rect((int)arg1, (GUI_Rect*)arg2);
     case Syscall::SC_read_tsc:
         return current->sys$read_tsc((dword*)arg1, (dword*)arg2);
+    case Syscall::SC_gui_notify_paint_finished:
+        return current->gui$notify_paint_finished((int)arg1, (const GUI_Rect*)arg2);
     default:
         kprintf("<%u> int0x80: Unknown function %u requested {%x, %x, %x}\n", current->pid(), function, arg1, arg2, arg3);
         break;

Kernel/Syscall.h

@@ -80,6 +80,7 @@
     __ENUMERATE_SYSCALL(gui_set_window_title) \
     __ENUMERATE_SYSCALL(gui_get_window_rect) \
     __ENUMERATE_SYSCALL(gui_set_window_rect) \
+    __ENUMERATE_SYSCALL(gui_notify_paint_finished) \
 
 
 #ifdef SERENITY

LibC/gui.cpp

@@ -50,3 +50,9 @@ int gui_set_window_rect(int window_id, const GUI_Rect* rect)
     int rc = syscall(SC_gui_set_window_rect, window_id, rect);
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
+
+int gui_notify_paint_finished(int window_id, const GUI_Rect* rect)
+{
+    int rc = syscall(SC_gui_notify_paint_finished, window_id, rect);
+    __RETURN_WITH_ERRNO(rc, rc, -1);
+}

LibC/gui.h

@@ -7,6 +7,7 @@ __BEGIN_DECLS
 
 int gui_create_window(const GUI_WindowParameters*);
 int gui_invalidate_window(int window_id, const GUI_Rect*);
+int gui_notify_paint_finished(int window_id, const GUI_Rect*);
 int gui_get_window_backing_store(int window_id, GUI_WindowBackingStoreInfo*);
 int gui_release_window_backing_store(void* backing_store_id);
 int gui_get_window_title(int window_id, char*, size_t);

LibGUI/GEventLoop.cpp

@@ -134,7 +134,7 @@ void GEventLoop::wait_for_event()
         }
         switch (event.type) {
         case GUI_Event::Type::Paint:
-            dbgprintf("WID=%x Paint [%d,%d %dx%d]\n", event.window_id, event.paint.rect.location.x, event.paint.rect.location.y, event.paint.rect.size.width, event.paint.rect.size.height); break;
+            dbgprintf("WID=%x Paint [%d,%d %dx%d]\n", event.window_id, event.paint.rect.location.x, event.paint.rect.location.y, event.paint.rect.size.width, event.paint.rect.size.height);
             handle_paint_event(event, *window);
             break;
         case GUI_Event::Type::MouseDown:

LibGUI/GWidget.cpp

@@ -106,7 +106,7 @@ void GWidget::update()
     if (m_has_pending_paint_event)
         return;
     m_has_pending_paint_event = true;
-    GEventLoop::main().post_event(w, make<GPaintEvent>(relative_rect()));
+    w->update(relative_rect());
 }
 
 GWidget::HitTestResult GWidget::hit_test(int x, int y)

LibGUI/GWindow.cpp

@@ -49,11 +49,18 @@ GWindow::~GWindow()
 void GWindow::set_title(String&& title)
 {
     dbgprintf("GWindow::set_title \"%s\"\n", title.characters());
-    GUI_WindowParameters params;
     int rc = gui_set_window_title(m_window_id, title.characters(), title.length());
     ASSERT(rc == 0);
 }
 
+String GWindow::title() const
+{
+    char buffer[256];
+    int rc = gui_get_window_title(m_window_id, buffer, sizeof(buffer));
+    ASSERT(rc >= 0);
+    return String(buffer, rc);
+}
+
 void GWindow::set_rect(const Rect& a_rect)
 {
     dbgprintf("GWindow::set_rect! %d,%d %dx%d\n", a_rect.x(), a_rect.y(), a_rect.width(), a_rect.height());
@@ -85,7 +92,7 @@ void GWindow::event(GEvent& event)
             rect = m_main_widget->rect();
         m_main_widget->event(*make<GPaintEvent>(rect));
         GUI_Rect gui_rect = rect;
-        int rc = gui_invalidate_window(m_window_id, &gui_rect);
+        int rc = gui_notify_paint_finished(m_window_id, &gui_rect);
         ASSERT(rc == 0);
     }
 
@@ -105,9 +112,11 @@ void GWindow::show()
 {
 }
 
-void GWindow::update()
+void GWindow::update(const Rect& a_rect)
 {
-    GEventLoop::main().post_event(this, make<GPaintEvent>());
+    GUI_Rect rect = a_rect;
+    int rc = gui_invalidate_window(m_window_id, a_rect.is_null() ? nullptr : &rect);
+    ASSERT(rc == 0);
 }
 
 void GWindow::set_main_widget(GWidget* widget)

LibGUI/GWindow.h

@@ -16,6 +16,7 @@ public:
 
     int window_id() const { return m_window_id; }
 
+    String title() const;
     void set_title(String&&);
 
     int x() const { return rect().x(); }
@@ -40,7 +41,7 @@ public:
 
     void show();
 
-    void update();
+    void update(const Rect& = Rect());
 
 private:
     RetainPtr<GraphicsBitmap> m_backing;

SharedGraphics/GraphicsBitmap.cpp

@@ -18,18 +18,16 @@ GraphicsBitmap::GraphicsBitmap(Process& process, const Size& size)
     , m_pitch(size.width() * sizeof(RGBA32))
     , m_client_process(&process)
 {
+    InterruptDisabler disabler;
     size_t size_in_bytes = size.width() * size.height() * sizeof(RGBA32);
     auto vmo = VMObject::create_anonymous(size_in_bytes);
     m_client_region = process.allocate_region_with_vmo(LinearAddress(), size_in_bytes, vmo.copyRef(), 0, "GraphicsBitmap (client)", true, true);
     m_client_region->set_shared(true);
     m_client_region->commit();
+    auto& server = WSEventLoop::the().server_process();
+    m_server_region = server.allocate_region_with_vmo(LinearAddress(), size_in_bytes, move(vmo), 0, "GraphicsBitmap (server)", true, false);
+    m_server_region->set_shared(true);
 
-    {
-        auto& server = WSEventLoop::the().server_process();
-        InterruptDisabler disabler;
-        m_server_region = server.allocate_region_with_vmo(LinearAddress(), size_in_bytes, move(vmo), 0, "GraphicsBitmap (server)", true, false);
-        m_server_region->set_shared(true);
-    }
     m_data = (RGBA32*)m_server_region->laddr().as_ptr();
 }
 #endif

Terminal/Terminal.cpp

@@ -88,7 +88,7 @@ Terminal::Line::Line(word columns)
 {
     characters = new byte[length];
     attributes = new Attribute[length];
-    needs_invalidation = false;
+    did_paint = false;
     memset(characters, ' ', length);
 }
 
@@ -603,7 +603,7 @@ void Terminal::paint()
     Painter painter(*m_backing);
 
     for (size_t i = 0; i < rows(); ++i)
-        line(i).needs_invalidation = false;
+        line(i).did_paint = false;
 
     if (m_rows_to_scroll_backing_store && m_rows_to_scroll_backing_store < m_rows) {
         int first_scanline = m_inset;
@@ -630,7 +630,7 @@ void Terminal::paint()
             painter.fill_rect(row_rect(row), line.attributes[0].background_color);
         for (word column = 0; column < m_columns; ++column) {
             auto& attribute = line.attributes[column];
-            line.needs_invalidation = true;
+            line.did_paint = true;
             char ch = line.characters[column];
             auto character_rect = glyph_rect(row, column);
             if (!has_only_one_background_color) {
@@ -649,7 +649,7 @@ void Terminal::paint()
     else
         painter.draw_rect(cursor_rect, Color::MidGray);
 
-    line(m_cursor_row).needs_invalidation = true;
+    line(m_cursor_row).did_paint = true;
 
     if (m_belling) {
         m_need_full_invalidation = true;
@@ -657,23 +657,38 @@ void Terminal::paint()
     }
 
     if (m_need_full_invalidation) {
-        invalidate_window();
+        did_paint();
         m_need_full_invalidation = false;
         return;
     }
 
-    Rect invalidation_rect;
+    Rect painted_rect;
     for (int i = 0; i < m_rows; ++i) {
-        if (line(i).needs_invalidation)
-            invalidation_rect = invalidation_rect.united(row_rect(i));
+        if (line(i).did_paint)
+            painted_rect = painted_rect.united(row_rect(i));
     }
-    invalidate_window(invalidation_rect);
+    did_paint(painted_rect);
 }
 
-void Terminal::invalidate_window(const Rect& a_rect)
+void Terminal::did_paint(const Rect& a_rect)
 {
     GUI_Rect rect = a_rect;
-    int rc = gui_invalidate_window(m_window_id, a_rect.is_null() ? nullptr : &rect);
+    int rc = gui_notify_paint_finished(m_window_id, a_rect.is_null() ? nullptr : &rect);
+    if (rc < 0) {
+        perror("gui_notify_paint_finished");
+        exit(1);
+    }
+}
+
+void Terminal::update()
+{
+    Rect rect;
+    for (int i = 0; i < m_rows; ++i) {
+        if (line(i).did_paint)
+            rect = rect.united(row_rect(i));
+    }
+    GUI_Rect gui_rect = rect;
+    int rc = gui_invalidate_window(m_window_id, rect.is_null() ? nullptr : &gui_rect);
     if (rc < 0) {
         perror("gui_invalidate_window");
         exit(1);
@@ -695,7 +710,7 @@ void Terminal::set_in_active_window(bool b)
         return;
     m_in_active_window = b;
     invalidate_cursor();
-    paint();
+    update();
 }
 
 void Terminal::invalidate_cursor()

Terminal/Terminal.h

@@ -18,6 +18,7 @@ public:
     void on_char(byte);
 
     void set_in_active_window(bool);
+    void update();
 
 private:
     Font& font() { return *m_font; }
@@ -25,6 +26,7 @@ private:
     void set_cursor(unsigned row, unsigned column);
     void put_character_at(unsigned row, unsigned column, byte ch);
     void invalidate_cursor();
+    void did_paint(const Rect& = Rect());
     void invalidate_window(const Rect& = Rect());
     void set_window_title(const String&);
 
@@ -67,7 +69,7 @@ private:
         bool has_only_one_background_color() const;
         byte* characters { nullptr };
         Attribute* attributes { nullptr };
-        bool needs_invalidation { false };
+        bool did_paint { false };
         bool dirty { false };
         word length { 0 };
     };

Terminal/main.cpp

@@ -77,7 +77,7 @@ int main(int, char**)
 
     Terminal terminal;
     terminal.create_window();
-    terminal.paint();
+    terminal.update();
 
     for (;;) {
         fd_set rfds;
@@ -100,7 +100,7 @@ int main(int, char**)
             assert(nread != 0);
             for (ssize_t i = 0; i < nread; ++i)
                 terminal.on_char(buffer[i]);
-            terminal.paint();
+            terminal.update();
         }
 
         if (FD_ISSET(event_fd, &rfds)) {

Userland/guitest.cpp

@@ -8,7 +8,7 @@
 #include <Kernel/Syscall.h>
 #include <SharedGraphics/GraphicsBitmap.h>
 #include <SharedGraphics/Painter.h>
-#include "gui.h"
+#include <LibC/gui.h>
 
 static void paint(GraphicsBitmap& bitmap, int width, int height);
 
@@ -68,8 +68,12 @@ int main(int argc, char** argv)
         case GUI_Event::Type::WindowDeactivated: dbgprintf("WID=%x WindowDeactivated\n", event.window_id); break;
         }
 
-        if (event.type == GUI_Event::Type::MouseDown) {
+        if (event.type == GUI_Event::Type::Paint) {
             paint(*bitmap, backing.size.width, backing.size.height);
+            gui_notify_paint_finished(window_id, nullptr);
+        }
+
+        if (event.type == GUI_Event::Type::MouseDown) {
             gui_invalidate_window(window_id, nullptr);
         }
 

WindowServer/WSEventLoop.cpp

@@ -94,6 +94,21 @@ void WSEventLoop::post_event(WSEventReceiver* receiver, OwnPtr<WSEvent>&& event)
         }
     }
 
+    if (event->type() == WSEvent::Paint) {
+        auto& invalidation_event = static_cast<WSPaintEvent&>(*event);
+        for (auto& queued_event : m_queued_events) {
+            if (receiver == queued_event.receiver && queued_event.event->type() == WSEvent::Paint) {
+                auto& queued_invalidation_event = static_cast<WSPaintEvent&>(*queued_event.event);
+                if (queued_invalidation_event.rect().is_empty() || queued_invalidation_event.rect().contains(invalidation_event.rect())) {
+#ifdef WSEVENTLOOP_DEBUG
+                    dbgprintf("Swallow WM_Paint\n");
+#endif
+                    return;
+                }
+            }
+        }
+    }
+
     m_queued_events.append({ receiver, move(event) });
 
     if (current != m_server_process)