StatusView: compute font size based on scrollbar size

Compute a font size that just fits the available space, instead of using
an arbitrary scaling. This makes the code adjust to any font and any UI
size.

Select the appropriate font using a binary search, which will need only
a few attempts (I think 6 font sizes will be tried at the default
config)

Change-Id: Ie3b8678678c0d940981f1785418aa8ab354d01c5
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3893
Reviewed-by: waddlesplash <[email protected]>
Tested-by: Commit checker robot <[email protected]>

headers/private/shared/StatusView.h

@@ -0,0 +1,5 @@
+namespace BPrivate {
+
+void AdoptScrollBarFontSize(BView*);
+
+} // namespace BPrivate

src/apps/stylededit/StatusView.cpp

@@ -9,6 +9,7 @@
 
 
 #include "StatusView.h"
+#include <StatusView.h>
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -63,7 +64,7 @@ void
 StatusView::AttachedToWindow()
 {
 	SetFont(be_plain_font);
-	SetFontSize(ceilf(be_plain_font->Size() * 0.83f));
+	BPrivate::AdoptScrollBarFontSize(this);
 
 	BMessage message(UPDATE_STATUS);
 	message.AddInt32("line", 1);

src/kits/shared/Jamfile

@@ -59,6 +59,7 @@ for architectureObject in [ MultiArchSubDirSetup ] {
 			SettingsHandler.cpp
 			SettingsMessage.cpp
 			ShakeTrackingFilter.cpp
+			StatusView.cpp
 			StringForRate.cpp
 			StringForSize.cpp
 			StripeView.cpp

src/kits/shared/StatusView.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2021, Pascal R. G. Abresch, [email protected].
+ * Distributed under the terms of the MIT License.
+ */
+
+#include <ControlLook.h>
+#include <View.h>
+
+
+namespace BPrivate {
+
+
+void
+AdoptScrollBarFontSize(BView* view)
+{
+	float maxSize = be_control_look->GetScrollBarWidth();
+	BFont testFont = be_plain_font;
+	float currentSize;
+	font_height fontHeight;
+
+	float minFontSize = 0.0f;
+	float maxFontSize = 48.0f;
+
+	while (maxFontSize - minFontSize > 1.0f) {
+		float midFontSize = (maxFontSize + minFontSize) / 2.0f;
+
+		testFont.SetSize(midFontSize);
+		testFont.GetHeight(&fontHeight);
+		currentSize = fontHeight.ascent + fontHeight.descent;
+
+		if (currentSize > maxSize)
+			maxFontSize = midFontSize;
+		else
+			minFontSize = midFontSize;
+	}
+
+	view->SetFontSize(minFontSize);
+}
+
+
+} // namespace BPrivate