Fix cursor positioning and unintentionally selected text.

[tools400]

Bug fixes

• Fixed unexpected text selection.
  Steps to reproduce the problem:
  • Select Send New Message... on a given queue.
  • Select the Payload tab.
  • Select type Bytes.
  • Click Import... to open the Select File dialog.
  • Ensure that the Select File dialog is placed over the hex editor area of the message editor.
    Actually the file that will be selected, must be over the hex editor area of the message editor.
  • Important: select the file with a mouse double-click.
  • The bytes displayed in the hex editor will be selected from the first byte to the last byte. The
    last byte is the byte where the double-click in the Select File dialog occurred.
• Fixed problem, that the cursor was not correctly positioned in the "Bytes" message editor on a mouse click.
  Steps to reproduce the problem:
  • Select Send New Message... on a given queue.
  • Select the Payload tab.
  • Select type Bytes.
  • Import a message from the file system.
  • Click on the first byte of the message editor. Cursor is correctly positioned.
  • Click on the eight byte of the message editor. Cursor is positioned on the seventh byte.
  • Click on the sixteenth byte of the message editor. Cursor is positioned on the thirteenth byte.
  • Reason: CHAR_HEIGHT and CHAR_WIDTH are set to fix values instead of being calculated depending on the font.