The Old New Thing

Code - The Old New Thing

Answer to exercise

August 15, 2003 Aug 15, 2003 08/15/03
Raymond Chen
The WM_SIZING handler intercepts only interactive resizing. If the user right-clicks the taskbar and selects "Cascade Windows", this resizes the window directly without going through the interactive WM_SIZING step...

Scrollbars part 8 – Integral interactive resizing

August 13, 2003 Aug 13, 2003 08/13/03
Raymond Chen
Enforcing integrality solves the fractional-line problem, but notice that when you grab the top or bottom edge and resize the window, the resize feedback doesn't match the actual window you get back if you drag the window to a non-integral size. (You may need to turn off full window drag to see this effect...

Scrollbars part 7 – Integrality

August 11, 2003 Aug 11, 2003 08/11/03
Raymond Chen
If you play around with resizing the window, you can get a fractional line to appear at the bottom of the screen. This is not normally a problem until you scroll to the very end of the list, say, by pressing the key, at which point an ugly blank space appears at the bottom. This ugly blank space is ...

Answers to exercises

August 11, 2003 Aug 11, 2003 08/11/03
Raymond Chen
What is the significance of the cast in the computation of ? It isn't. I got the question wrong. The real question should have been "What is the significance of the cast in the computation of ?" The answer is to ensure that the computation is performed with signed integers ...

A subtlety in the keyboard code

August 7, 2003 Aug 7, 2003 08/7/03
Raymond Chen
I neglected to call it out explicitly in the text for Part 5:  Notice that I use cRepeat to determine how many lines/pages to scroll.  This allows us to scroll the correct amount even if we are falling behind on input processing and are missing some autorepeats...

Scrollbars bart 6 – The wheel

August 7, 2003 Aug 7, 2003 08/7/03
Raymond Chen
The mouse wheel is tricky because the mouse wheel UI guidelines indicate that you should scroll by a user-specified amount for each "click" of the mouse, where one click is mouse units (called a "detent"). There are two subtle points about the above requirement: First, that the amount of scrolling is a ...

Keyboard accessibility for scrollbars

August 5, 2003 Aug 5, 2003 08/5/03
Raymond Chen
Note that so far, the scrollbar is accessible only with the mouse. Our next step is to add keyboard access to the scrollbar. Fortunately, this is not all that difficult. We merely map some keystrokes to equivalent scrollbar actions. Note that this doesn't make our sample program fully accessible; this ...

Answer to previous exercise on proportional scrollbars

August 5, 2003 Aug 5, 2003 08/5/03
Raymond Chen
If you look at the WM_VSCROLL message, you'll see that the scroll position is a 16-bit value. So if the number of entries is more then 65535, you won't be able to use the scroll thumb to get to the ones at the end. Try it: Change the value of g_cItems to 100000 and watch what happens. The fix is to ignore the passed to the message and ...

Scrollbars, part 4: Adding a proportional scrollbar

July 31, 2003 Jul 31, 2003 07/31/03
Raymond Chen
To obtain a proportional scrollbar, you need to tell Windows the minimum and maximum values covered by the scrollbar, the current scrollbar position, and the size of the scrollbar thumb (called the "page size"). One annoyance of the way scrollbars are set up is that the maximum value is attainable. This ...