CharacterMap: several fixes to char. view scroll

* Select items in the encoding list by block identifier rather than
list index (there are holes in the list)
* Scroll to the start of the list when the application starts
* Add and use IsBlockVisible to detect when we need to make a block
visible, avoiding unwanted scrollings in some cases with the previous
method of testing for only one character in the block.

Signed-off-by: Adrien Destugues <pulkomandy@gmail.com>

Fixes some problems with previous enhancements from #3651.

src/apps/charactermap/CharacterView.cpp

@@ -38,6 +38,7 @@ CharacterView::CharacterView(const char* name)
 	fCharacterFont.SetSize(fCharacterFont.Size() * 1.5f);
 
 	_UpdateFontSize();
+	DoLayout();
 }
 
 
@@ -108,10 +109,10 @@ CharacterView::IsShowingBlock(int32 blockIndex) const
 void
 CharacterView::ScrollToBlock(int32 blockIndex)
 {
-	// don't scroll if the selected character is already in view.
+	// don't scroll if the selected block is already in view.
 	// this prevents distracting jumps when crossing a block 
 	// boundary in the character view.
-	if (IsCharacterVisible(fCurrentCharacter))
+	if (IsBlockVisible(blockIndex))   
 		return;
 		
 	if (blockIndex < 0)
@@ -141,6 +142,19 @@ CharacterView::IsCharacterVisible(uint32 c) const
 }
 
 
+bool
+CharacterView::IsBlockVisible(int32 block) const
+{
+	int32 topBlock = _BlockAt(BPoint(Bounds().left, Bounds().top));
+	int32 bottomBlock = _BlockAt(BPoint(Bounds().right, Bounds().bottom)); 
+
+	if (block >= topBlock && block <= bottomBlock) 
+		return true;
+		
+	return false;
+}
+
+
 /*static*/ void
 CharacterView::UnicodeToUTF8(uint32 c, char* text, size_t textSize)
 {

src/apps/charactermap/CharacterView.h

@@ -33,6 +33,7 @@ public:
 			void			ScrollToBlock(int32 blockIndex);
 			void			ScrollToCharacter(uint32 c);
 			bool			IsCharacterVisible(uint32 c) const;
+			bool			IsBlockVisible(int32 block) const;
 
 	static	void			UnicodeToUTF8(uint32 c, char* text,
 								size_t textSize);

src/apps/charactermap/CharacterWindow.cpp

@@ -275,6 +275,8 @@ CharacterWindow::CharacterWindow()
 	fUnicodeBlockView->SetTarget(this);
 
 	fFilterControl->MakeFocus();
+	
+	fUnicodeBlockView->SelectBlockForCharacter(0);
 }
 
 

src/apps/charactermap/UnicodeBlockView.cpp

@@ -133,7 +133,13 @@ UnicodeBlockView::SelectBlockForCharacter(uint32 character)
 			break;
 		}
 
-		Select(i);
+		BlockListItem* block = fBlocks.ItemAt(i);
+		
+		int32 blockNum = IndexOf(block);
+		
+		if (blockNum >= 0) {
+			Select(blockNum);
 			ScrollToSelection();
 		}
+	}
 }