various: allow setting footage aspect ratios

We had support for detecting aspect ratios and respecting them in the
render, but this allows people to not only see the aspect ratio in use,
but also override it with their own.

app/widget/viewer/viewer.cpp

@@ -32,6 +32,7 @@
 
 #include "audio/audiomanager.h"
 #include "common/power.h"
+#include "common/ratiodialog.h"
 #include "common/timecodefunctions.h"
 #include "config/config.h"
 #include "project/item/sequence/sequence.h"
@@ -397,6 +398,8 @@ FramePtr DecodeCachedImage(const QString &fn, const rational& time)
 
   if (frame) {
     frame->set_timestamp(time);
+  } else {
+    qWarning() << "Tried to load cached frame from file but it was null";
   }
 
   return frame;
@@ -743,45 +746,14 @@ void ViewerWidget::ContextMenuSetSafeMargins()
 
 void ViewerWidget::ContextMenuSetCustomSafeMargins()
 {
-  QString s;
+  bool ok;
 
-  forever {
-    bool ok;
+  double new_ratio = GetFloatRatioFromUser(this,
+                                           tr("Safe Margins"),
+                                           &ok);
 
-    s = QInputDialog::getText(this,
-                              tr("Safe Margins"),
-                              tr("Enter custom ratio (e.g. \"4:3\", \"16/9\", etc.):"),
-                              QLineEdit::Normal,
-                              s,
-                              &ok);
-
-    if (!ok) {
-      // User cancelled dialog, do nothing
-      return;
-    }
-
-    QStringList ratio_components = s.split(QRegExp(QStringLiteral(":|;|\\/")));
-
-    if (ratio_components.size() == 2) {
-      bool numer_ok, denom_ok;
-
-      double num = ratio_components.at(0).toDouble(&numer_ok);
-      double den = ratio_components.at(1).toDouble(&denom_ok);
-
-      if (numer_ok
-          && denom_ok
-          && num > 0) {
-        // Exit loop and set this ratio
-        context_menu_widget_->SetSafeMargins(ViewerSafeMarginInfo(true, num / den));
-        return;
-      }
-    }
-
-    QMessageBox::warning(this,
-                         tr("Invalid custom ratio"),
-                         tr("Failed to parse \"%1\" into an aspect ratio. Please format a "
-                            "rational fraction with a ':' or a '/' separator.").arg(s),
-                         QMessageBox::Ok);
+  if (ok) {
+    context_menu_widget_->SetSafeMargins(ViewerSafeMarginInfo(true, new_ratio));
   }
 }