Merge bitcoin-core/gui#116: Fix unreasonable default size of the main window without loaded wallets

7b2e42ecc4 qt: Add WalletFrame::sizeHint (Hennadii Stepanov)

Pull request description:

  This PR fixes a bug in master (d67883d01e) and in 0.20.1 that could be easily reproduced with
  ```
  $ src/qt/bitcoin-qt -regtest -resetguisettings -nowallet
  ```

  ![Screenshot from 2020-10-25 21-21-27](https://user-images.githubusercontent.com/32963518/97117179-b1800100-170a-11eb-87c9-3120d39b9455.png)
  ![Screenshot from 2020-10-25 21-23-32](https://user-images.githubusercontent.com/32963518/97117186-b644b500-170a-11eb-8b5d-234ff7205003.png)

  **With this PR:**

  ![Screenshot from 2020-10-25 21-20-35](https://user-images.githubusercontent.com/32963518/97117226-f441d900-170a-11eb-8d66-98b7718a2bb1.png)
  ![Screenshot from 2020-10-25 21-23-03](https://user-images.githubusercontent.com/32963518/97117232-f99f2380-170a-11eb-85ed-c7b5ece926b2.png)

  ---

  Fix #104
  Fix #113

  This PR is an alternative to #107 without [hard-coding a size in pixels](https://github.com/bitcoin-core/gui/pull/107#discussion_r511474021).

ACKs for top commit:
  jonasschnelli:
    Tested ACK 7b2e42ecc4 - I can confirm this fixes #104 (Ubuntu 20.04 - HiDPI 200%).

Tree-SHA512: eb0692dbeb3befdeecca0e41534c9783eab6637c14cc4f170ee42619235884f9354f8d22a10c20c08cc89dc5340a60b7dfa2523c12e64b3386b3fd2c6d5f934e

src/qt/walletframe.cpp

@@ -2,12 +2,13 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <qt/createwalletdialog.h>
-#include <qt/walletcontroller.h>
 #include <qt/walletframe.h>
-#include <qt/walletmodel.h>
 
 #include <qt/bitcoingui.h>
+#include <qt/createwalletdialog.h>
+#include <qt/overviewpage.h>
+#include <qt/walletcontroller.h>
+#include <qt/walletmodel.h>
 #include <qt/walletview.h>
 
 #include <cassert>
@@ -18,10 +19,11 @@
 #include <QPushButton>
 #include <QVBoxLayout>
 
-WalletFrame::WalletFrame(const PlatformStyle *_platformStyle, BitcoinGUI *_gui) :
-    QFrame(_gui),
-    gui(_gui),
-    platformStyle(_platformStyle)
+WalletFrame::WalletFrame(const PlatformStyle* _platformStyle, BitcoinGUI* _gui)
+    : QFrame(_gui),
+      gui(_gui),
+      platformStyle(_platformStyle),
+      m_size_hint(OverviewPage{platformStyle, nullptr}.sizeHint())
 {
     // Leave HBox hook for adding a list view later
     QHBoxLayout *walletFrameLayout = new QHBoxLayout(this);

src/qt/walletframe.h

@@ -45,6 +45,8 @@ public:
 
     void showOutOfSyncWarning(bool fShow);
 
+    QSize sizeHint() const override { return m_size_hint; }
+
 Q_SIGNALS:
     /** Notify that the user has requested more information about the out-of-sync warning */
     void requestedSyncWarningInfo();
@@ -59,6 +61,8 @@ private:
 
     const PlatformStyle *platformStyle;
 
+    const QSize m_size_hint;
+
 public:
     WalletView* currentWalletView() const;
     WalletModel* currentWalletModel() const;