QtBase: use erase and std::remove_if with QList and QVector

... instead of using removeAt in a loop, with quadratic complexity.

Change-Id: I38b49e56b12c396db9fc0f1b75d8fb43c503a7f6
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/itemmodels/qitemselectionmodel.cpp

@@ -1717,15 +1717,15 @@ const QItemSelection QItemSelectionModel::selection() const
     Q_D(const QItemSelectionModel);
     QItemSelection selected = d->ranges;
     selected.merge(d->currentSelection, d->currentCommand);
-    int i = 0;
     // make sure we have no invalid ranges
     // ###  should probably be handled more generic somewhere else
-    while (i<selected.count()) {
-        if (selected.at(i).isValid())
-            ++i;
-        else
-            (selected.removeAt(i));
-    }
+    auto isNotValid = [](const QItemSelectionRange& range) {
+        return !range.isValid();
+    };
+
+    selected.erase(std::remove_if(selected.begin(), selected.end(),
+                                  isNotValid),
+                   selected.end());
     return selected;
 }
 

src/gui/opengl/qopenglengineshadermanager.cpp

@@ -45,6 +45,8 @@
 #include <QtGui/private/qopenglcontext_p.h>
 #include <QtCore/qthreadstorage.h>
 
+#include <algorithm>
+
 #if defined(QT_DEBUG)
 #include <QMetaEnum>
 #endif
@@ -475,15 +477,16 @@ QOpenGLEngineShaderProg *QOpenGLEngineSharedShaders::findProgramInCache(const QO
 
 void QOpenGLEngineSharedShaders::cleanupCustomStage(QOpenGLCustomShaderStage* stage)
 {
-    // Remove any shader programs which has this as the custom shader src:
-    for (int i = 0; i < cachedPrograms.size(); ++i) {
-        QOpenGLEngineShaderProg *cachedProg = cachedPrograms[i];
+    auto hasStageAsCustomShaderSouce = [stage](QOpenGLEngineShaderProg *cachedProg) -> bool {
         if (cachedProg->customStageSource == stage->source()) {
             delete cachedProg;
-            cachedPrograms.removeAt(i);
-            i--;
+            return true;
         }
-    }
+        return false;
+    };
+    cachedPrograms.erase(std::remove_if(cachedPrograms.begin(), cachedPrograms.end(),
+                                        hasStageAsCustomShaderSouce),
+                         cachedPrograms.end());
 }
 
 

src/gui/text/qtextdocumentlayout.cpp

@@ -2901,14 +2901,12 @@ static void markFrames(QTextFrame *current, int from, int oldLength, int length)
         return;
 
     QTextFrameData *fd = data(current);
-    for (int i = 0; i < fd->floats.size(); ++i) {
-        QTextFrame *f = fd->floats[i];
-        if (!f) {
-            // float got removed in editing operation
-            fd->floats.removeAt(i);
-            --i;
-        }
-    }
+    // float got removed in editing operation
+    QTextFrame *null = nullptr; // work-around for (at least) MSVC 2012 emitting
+                                // warning C4100 for its own header <algorithm>
+                                // when passing nullptr directly to std::remove
+    fd->floats.erase(std::remove(fd->floats.begin(), fd->floats.end(), null),
+                     fd->floats.end());
 
     fd->layoutDirty = true;
     fd->sizeDirty = true;

src/opengl/gl2paintengineex/qglengineshadermanager.cpp

@@ -48,6 +48,8 @@
 #include <QMetaEnum>
 #endif
 
+#include <algorithm>
+
 // #define QT_GL_SHARED_SHADER_DEBUG
 
 QT_BEGIN_NAMESPACE
@@ -472,15 +474,16 @@ QGLEngineShaderProg *QGLEngineSharedShaders::findProgramInCache(const QGLEngineS
 
 void QGLEngineSharedShaders::cleanupCustomStage(QGLCustomShaderStage* stage)
 {
-    // Remove any shader programs which has this as the custom shader src:
-    for (int i = 0; i < cachedPrograms.size(); ++i) {
-        QGLEngineShaderProg *cachedProg = cachedPrograms[i];
+    auto hasStageAsCustomShaderSouce = [stage](QGLEngineShaderProg *cachedProg) -> bool {
         if (cachedProg->customStageSource == stage->source()) {
             delete cachedProg;
-            cachedPrograms.removeAt(i);
-            i--;
+            return true;
         }
-    }
+        return false;
+    };
+    cachedPrograms.erase(std::remove_if(cachedPrograms.begin(), cachedPrograms.end(),
+                                        hasStageAsCustomShaderSouce),
+                         cachedPrograms.end());
 }
 
 

src/plugins/platforms/ios/qiosmenu.mm

@@ -48,6 +48,9 @@
 #include "qiosintegration.h"
 #include "qiostextresponder.h"
 
+#include <algorithm>
+#include <iterator>
+
 // m_currentMenu points to the currently visible menu.
 // Only one menu will be visible at a time, and if a second menu
 // is shown on top of a first, the first one will be told to hide.
@@ -525,14 +528,10 @@ bool QIOSMenu::eventFilter(QObject *obj, QEvent *event)
 
 QIOSMenuItemList QIOSMenu::visibleMenuItems() const
 {
-    QIOSMenuItemList visibleMenuItems = m_menuItems;
-
-    for (int i = visibleMenuItems.count() - 1; i >= 0; --i) {
-        QIOSMenuItem *item = visibleMenuItems.at(i);
-        if (!item->m_enabled || !item->m_visible || item->m_separator)
-            visibleMenuItems.removeAt(i);
-    }
-
+    QIOSMenuItemList visibleMenuItems;
+    visibleMenuItems.reserve(m_menuItems.size());
+    std::copy_if(m_menuItems.begin(), m_menuItems.end(), std::back_inserter(visibleMenuItems),
+                 [](QIOSMenuItem *item) { return item->m_enabled && item->m_visible && !item->m_separator; });
     return visibleMenuItems;
 }
 

src/widgets/itemviews/qabstractitemview.cpp

@@ -68,6 +68,8 @@
 #  include <qscroller.h>
 #endif
 
+#include <algorithm>
+
 QT_BEGIN_NAMESPACE
 
 QAbstractItemViewPrivate::QAbstractItemViewPrivate()
@@ -4459,10 +4461,12 @@ QModelIndexList QAbstractItemViewPrivate::selectedDraggableIndexes() const
 {
     Q_Q(const QAbstractItemView);
     QModelIndexList indexes = q->selectedIndexes();
-    for(int i = indexes.count() - 1 ; i >= 0; --i) {
-        if (!isIndexDragEnabled(indexes.at(i)))
-            indexes.removeAt(i);
-    }
+    auto isNotDragEnabled = [this](const QModelIndex &index) {
+        return !isIndexDragEnabled(index);
+    };
+    indexes.erase(std::remove_if(indexes.begin(), indexes.end(),
+                                 isNotDragEnabled),
+                  indexes.end());
     return indexes;
 }
 

src/widgets/styles/qwindowsstyle.cpp

@@ -71,6 +71,8 @@
 #include <private/qstylehelper_p.h>
 #include <private/qstyleanimation_p.h>
 
+#include <algorithm>
+
 QT_BEGIN_NAMESPACE
 
 #if defined(Q_OS_WIN)
@@ -159,12 +161,11 @@ bool QWindowsStyle::eventFilter(QObject *o, QEvent *e)
 
             // Alt has been pressed - find all widgets that care
             QList<QWidget *> l = widget->findChildren<QWidget *>();
-            for (int pos=0 ; pos < l.size() ; ++pos) {
-                QWidget *w = l.at(pos);
-                if (w->isWindow() || !w->isVisible() ||
-                    w->style()->styleHint(SH_UnderlineShortcut, 0, w))
-                    l.removeAt(pos);
-            }
+            auto ignorable = [](QWidget *w) {
+                return w->isWindow() || !w->isVisible()
+                        || w->style()->styleHint(SH_UnderlineShortcut, 0, w);
+            };
+            l.erase(std::remove_if(l.begin(), l.end(), ignorable), l.end());
             // Update states before repainting
             d->seenAlt.append(widget);
             d->alt_down = true;

src/widgets/widgets/qabstractbutton.cpp

@@ -188,15 +188,16 @@ QList<QAbstractButton *>QAbstractButtonPrivate::queryButtonList() const
 
     QList<QAbstractButton*>candidates = parent->findChildren<QAbstractButton *>();
     if (autoExclusive) {
-        for (int i = candidates.count() - 1; i >= 0; --i) {
-            QAbstractButton *candidate = candidates.at(i);
-            if (!candidate->autoExclusive()
+        auto isNoMemberOfMyAutoExclusiveGroup = [](QAbstractButton *candidate) {
+            return !candidate->autoExclusive()
 #ifndef QT_NO_BUTTONGROUP
                 || candidate->group()
 #endif
-                )
-                candidates.removeAt(i);
-        }
+                ;
+        };
+        candidates.erase(std::remove_if(candidates.begin(), candidates.end(),
+                                        isNoMemberOfMyAutoExclusiveGroup),
+                         candidates.end());
     }
     return candidates;
 }