Introduce a RequestGeometryBlocker in ShellClient

Summary:
The idea is to not send multiple resize requests to a client when we
know that we might have multiple geometry changes. E.g. when going
from maximized to restored the borders change and trigger a resize in
addition to the resize from switching to restored.

The implementation is inspired by the GeometryUpdateBlocker.

Reviewers: #kwin, #plasma_on_wayland

Subscribers: plasma-devel, kwin

Tags: #plasma_on_wayland, #kwin

Differential Revision: https://phabricator.kde.org/D1808

autotests/wayland/maximize_test.cpp

@@ -214,6 +214,15 @@ void TestMaximized::testMaximizedPassedToDeco()
     QCOMPARE(client->maximizeMode(), MaximizeMode::MaximizeRestore);
     QCOMPARE(maximizedChangedSpy.count(), 2);
     QCOMPARE(maximizedChangedSpy.last().first().toBool(), false);
+    QCOMPARE(bordersChangedSpy.count(), 2);
+    QVERIFY(decoration->borderTop() != 0);
+    QVERIFY(decoration->borderLeft() != 0);
+    QVERIFY(decoration->borderRight() != 0);
+    QVERIFY(decoration->borderBottom() != 0);
+
+    QVERIFY(sizeChangedSpy.wait());
+    QCOMPARE(sizeChangedSpy.count(), 2);
+    QCOMPARE(sizeChangedSpy.last().first().toSize(), QSize(100, 50));
 }
 
 void TestMaximized::testInitiallyMaximized()

shell_client.cpp

@@ -348,6 +348,7 @@ void ShellClient::createDecoration(const QRect &oldGeom)
         connect(decoration, &KDecoration2::Decoration::bordersChanged, this,
             [this]() {
                 GeometryUpdatesBlocker blocker(this);
+                RequestGeometryBlocker requestBlocker(this);
                 QRect oldgeom = geometry();
                 if (!isShade())
                     checkWorkspacePosition(oldgeom);
@@ -565,6 +566,7 @@ void ShellClient::changeMaximize(bool horizontal, bool vertical, bool adjust)
     }
     MaximizeMode oldMode = m_maximizeMode;
     StackingUpdatesBlocker blocker(workspace());
+    RequestGeometryBlocker geometryBlocker(this);
     // 'adjust == true' means to update the size only, e.g. after changing workspace size
     if (!adjust) {
         if (vertical)
@@ -801,10 +803,15 @@ bool ShellClient::isInputMethod() const
 
 void ShellClient::requestGeometry(const QRect &rect)
 {
+    if (m_requestGeometryBlockCounter != 0) {
+        m_blockedRequestGeometry = rect;
+        return;
+    }
     m_positionAfterResize.setPoint(rect.topLeft());
     if (m_shellSurface) {
         m_shellSurface->requestSize(rect.size() - QSize(borderLeft() + borderRight(), borderTop() + borderBottom()));
     }
+    m_blockedRequestGeometry = QRect();
 }
 
 void ShellClient::clientFullScreenChanged(bool fullScreen)

shell_client.h

@@ -172,6 +172,29 @@ private:
     bool m_transient = false;
     bool m_internal;
     qreal m_opacity = 1.0;
+
+    class RequestGeometryBlocker {
+    public:
+        RequestGeometryBlocker(ShellClient *client)
+            : m_client(client)
+        {
+            m_client->m_requestGeometryBlockCounter++;
+        }
+        ~RequestGeometryBlocker()
+        {
+            m_client->m_requestGeometryBlockCounter--;
+            if (m_client->m_requestGeometryBlockCounter == 0) {
+                if (m_client->m_blockedRequestGeometry.isValid()) {
+                    m_client->requestGeometry(m_client->m_blockedRequestGeometry);
+                }
+            }
+        }
+    private:
+        ShellClient *m_client;
+    };
+    friend class RequestGeometryBlocker;
+    int m_requestGeometryBlockCounter = 0;
+    QRect m_blockedRequestGeometry;
 };
 
 }