[Qt] keep scroll position in GUI console after changing font size

src/qt/forms/debugwindow.ui

@@ -480,7 +480,7 @@
             </size>
            </property>
            <property name="toolTip">
-            <string>Decrease Font Size</string>
+            <string>Decrease font size</string>
            </property>
            <property name="text">
             <string/>
@@ -512,7 +512,7 @@
             </size>
            </property>
            <property name="toolTip">
-            <string>Increase Font Size</string>
+            <string>Increase font size</string>
            </property>
            <property name="text">
             <string/>

src/qt/rpcconsole.cpp

@@ -490,8 +490,10 @@ void RPCConsole::setFontSize(int newSize)
     settings.setValue(fontSizeSettingsKey, consoleFontSize);
 
     // clear console (reset icon sizes, default stylesheet) and re-add the content
+    float oldPosFactor = 1.0 / ui->messagesWidget->verticalScrollBar()->maximum() * ui->messagesWidget->verticalScrollBar()->value();
     clear();
     ui->messagesWidget->setHtml(str);
+    ui->messagesWidget->verticalScrollBar()->setValue(oldPosFactor * ui->messagesWidget->verticalScrollBar()->maximum());
 }
 
 void RPCConsole::clear()