Screensaver: Set explicit min width for fSettingsView

Also make some new const variables to make some math more opaque
i.e. don't use as many magic constants.

This works great at 12pt font size, decenly at all other sizes. There is a
bit of jitter at 13pt and 24pt for some reason when moving from a default
settings view to another settings view.

src/preferences/screensaver/ScreenSaverWindow.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2014 Haiku, Inc. All rights reserved.
+ * Copyright 2003-2016 Haiku, Inc. All rights reserved.
  * Distributed under the terms of the MIT License.
  *
  * Authors:
@@ -30,7 +30,7 @@
 #include <File.h>
 #include <FindDirectory.h>
 #include <Font.h>
-#include <Layout.h>
+#include <GroupLayout.h>
 #include <LayoutBuilder.h>
 #include <ListItem.h>
 #include <ListView.h>
@@ -79,6 +79,10 @@ const int32 kMsgTurnOffSliderUpdate = 'TUup';
 const int32 kMsgFadeCornerChanged = 'fdcc';
 const int32 kMsgNeverFadeCornerChanged = 'nfcc';
 
+const float kWindowWidth = 446.0f;
+const float kWindowHeight = 325.0f;
+const float kDefaultItemSpacingAt12pt = 12.0f * 0.85;
+
 
 class TimeSlider : public BSlider {
 public:
@@ -572,6 +576,10 @@ ModulesView::ModulesView(const char* name, ScreenSaverSettings& settings)
 		fScreenSaversListView, 0, false, true);
 
 	fSettingsBox->SetLabel(B_TRANSLATE("Screensaver settings"));
+	fSettingsBox->SetExplicitMinSize(BSize(
+		floorf(be_control_look->DefaultItemSpacing()
+			* ((kWindowWidth - 157.0f) / kDefaultItemSpacingAt12pt)),
+		B_SIZE_UNSET));
 
 	BLayoutBuilder::Group<>(this, B_HORIZONTAL)
 		.SetInsets(B_USE_WINDOW_SPACING, B_USE_WINDOW_SPACING,
@@ -914,20 +922,20 @@ TabView::MouseDown(BPoint where)
 
 ScreenSaverWindow::ScreenSaverWindow()
 	:
-	BWindow(BRect(50, 50, 496, 375),
+	BWindow(BRect(50.0f, 50.0f, 50.0f + kWindowWidth, 50.0f + kWindowHeight),
 		B_TRANSLATE_SYSTEM_NAME("ScreenSaver"), B_TITLED_WINDOW,
 		B_ASYNCHRONOUS_CONTROLS | B_AUTO_UPDATE_SIZE_LIMITS)
 {
 	fSettings.Load();
 
-	fMinWidth = ceilf(std::max(446.0f,
-		be_control_look->DefaultItemSpacing() * 44.6f));
+	fMinWidth = floorf(be_control_look->DefaultItemSpacing()
+		* (kWindowWidth / kDefaultItemSpacingAt12pt));
 
 	font_height fontHeight;
 	be_plain_font->GetHeight(&fontHeight);
 	float textHeight = ceilf(fontHeight.ascent + fontHeight.descent);
 
-	fMinHeight = ceilf(std::max(325.0f, textHeight * 28));
+	fMinHeight = ceilf(std::max(kWindowHeight, textHeight * 28));
 
 	// Create the password editing window
 	fPasswordWindow = new PasswordWindow(fSettings);