Android: Place cursor correctly on screen when editing

When editing text the cursor is not placed correctly. So this
has been achieved by tricking Android into thinking that the
input area is only the line where the cursor is, so it is
forced to keep it on screen.

Fixes: QTBUG-91073
Pick-to: 5.15
Change-Id: Icc2e8315deb76ca1a84819d3fdceaa7b027b1174
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>

1 files changed, 41 insertions, 3 deletions

diff --git a/src/plugins/platforms/android/qandroidinputcontext.cpp b/src/plugins/platforms/android/qandroidinputcontext.cpp
index 29236667d3..378dfa03c8 100644
--- a/src/plugins/platforms/android/qandroidinputcontext.cpp
+++ b/src/plugins/platforms/android/qandroidinputcontext.cpp
@@ -47,6 +47,7 @@
 #include "qandroideventdispatcher.h"
 #include "qandroidinputcontext.h"
 #include "qandroidplatformintegration.h"
+#include "private/qhighdpiscaling_p.h"
 
 #include <QTextBoundaryFinder>
 #include <QTextCharFormat>
@@ -59,7 +60,6 @@
 #include <qthread.h>
 #include <qwindow.h>
 #include <qpa/qplatformwindow.h>
-
 QT_BEGIN_NAMESPACE
 
 namespace {
@@ -491,7 +491,7 @@ QAndroidInputContext::QAndroidInputContext()
     m_androidInputContext = this;
 
     QObject::connect(QGuiApplication::inputMethod(), &QInputMethod::cursorRectangleChanged,
-                     this, &QAndroidInputContext::updateSelectionHandles);
+                     this, &QAndroidInputContext::updateInputItemRectangle);
     QObject::connect(QGuiApplication::inputMethod(), &QInputMethod::anchorRectangleChanged,
                      this, &QAndroidInputContext::updateSelectionHandles);
     QObject::connect(QGuiApplication::inputMethod(), &QInputMethod::inputItemClipRectangleChanged, this, [this]{
@@ -889,12 +889,50 @@ void QAndroidInputContext::showInputPanel()
     else
         m_updateCursorPosConnection = connect(qGuiApp->focusObject(), SIGNAL(cursorPositionChanged()), this, SLOT(updateCursorPosition()));
 
-    QRect rect = screenInputItemRectangle();
+    QRect rect = cursorRect();
     QtAndroidInput::showSoftwareKeyboard(rect.left(), rect.top(), rect.width(), rect.height(),
+                                         screenInputItemRectangle().height(),
                                          query->value(Qt::ImHints).toUInt(),
                                          query->value(Qt::ImEnterKeyType).toUInt());
 }
 
+QRect QAndroidInputContext::cursorRect()
+{
+    QSharedPointer<QInputMethodQueryEvent> query = focusObjectInputMethodQuery();
+    // if single line, we do not want to mess with the editor's position, as we do not
+    // have to follow the cursor in vertical axis
+    if (query.isNull()
+        || (query->value(Qt::ImHints).toUInt() & Qt::ImhMultiLine) != Qt::ImhMultiLine)
+        return {};
+
+    auto im = qGuiApp->inputMethod();
+    if (!im)
+        return {};
+
+    const auto cursorRect= im->cursorRectangle().toRect();
+    QRect finalRect(inputItemRectangle().toRect());
+    const QWindow *window = qGuiApp->focusWindow();
+    const double pd = window
+        ? QHighDpiScaling::factor(window)
+        : QHighDpiScaling::factor(QtAndroid::androidPlatformIntegration()->screen());
+    finalRect.setY(cursorRect.y() * pd);
+    finalRect.setHeight(cursorRect.height() * pd);
+    //fiddle a bit with vert margins, so the tracking rectangle is not too tight.
+    finalRect += QMargins(0, cursorRect.height() / 4, 0, cursorRect.height() / 4);
+    return finalRect;
+}
+
+void QAndroidInputContext::updateInputItemRectangle()
+{
+    QRect rect = cursorRect();
+
+    if (!rect.isValid())
+        return;
+    QtAndroidInput::updateInputItemRectangle(rect.left(), rect.top(),
+                                             rect.width(), rect.height());
+    updateSelectionHandles();
+}
+
 void QAndroidInputContext::showInputPanelLater(Qt::ApplicationState state)
 {
     if (state != Qt::ApplicationActive)