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Dancing Checkboxes

Writing a window that will allow you to “set the day of the week”

Normally I write columns about the DataWindow or Appeon. This month though I ran into an interesting little logic problem and when I solved it I realized it was really a nice piece of code so, even though it is not in my normal genre I thought I'd share it.

I was tasked with allowing the user to pick a combination of days of the week with these specifications.

  1. The user may select no more than three days prior to today.
  2. The user may select no more than three days in the future.
  3. The user may not have both prior and future dates in the same group
  4. If there are not three days in the past available in this week then the week "wraps." That is to say, if the day is Monday then you only have Sunday as a past day in the week, but for our purposes Saturday and Friday would be considered past days of the same week.
  5. Repeat rule 4 for future days.

It was actually rules 4 and 5 that gave me fits. If it hadn't been for those rules this would be a straightforward thing. Rules 4 and 5 meant that I had to get really creative. Rules 4 and 5 stem from the fact that this is a means of selecting days for a report. The report may be historical or projected (future). They are only interested in four days at any time. Those four days being the current day and either up to three days in the past or future. In fact they aren't necessarily interested in today. They may only choose last Tuesday - as long as last Tuesday was not farther than three days in the past.

For the purposes of this article I am going to write a window that will allow you to "set the day of the week" so that we can test.

I created a small window and put seven checkboxes thereupon. They were named, predictably, cbx_Sunday, cbx_Monday, cbx_Tuesday, cbx_Wednesday, etc. Each of the checkbox controls were carefully sized to be just a little bit bigger than the text. I put each of them inside a group box that had the text attribute removed so it just looked like a 3D box. Then I aligned them horizontally, see Figure 1.

Here is where the problems with rules 4 and 5 become apparent. If today is Wednesday then everything looks and acts fine. We could have the previous three days selected with no problem. Look at Figure 2.

We are supposing in Figure 2 that today is June 25, 2012. We have Monday checked. Also Sunday is checked and that would be June 24. Sunday and Saturday are both checked and according to our rules they would be June 23 and June 22. However, if you look at Figure 2, does it appear that Saturday and Sunday are in the past? No, of course it doesn't. I found this to be deceptive and prone to user error. Clearly some creativity is required here.

My first idea was to let the checkboxes be moved so that the middle day of the seven was always in the middle. That way the days on the left are always in the past and the days on the right are always in the future. For my first attempt I made all the controls equal size, as big as the biggest, and then it was easy to just move them around.

The problem with this is that the display looked horrible. There was more space between Monday and Tuesday than Wednesday and Thursday. It just didn't look good, see Figure 3.

Compare the space between Wednesday and Thursday to the space between Friday and Saturday. Clearly this is inconsistent. We needed a better idea.

I went back to the original idea of having the controls just a little bit bigger than they needed to be. Now I couldn't use fixed positions for the x coordinate. I needed to generate the x coordinates. That meant that I could start where cbx_Sunday.x is but after that I need to put the second one at cbx_Sunday.x + cbx_Sunday.width + li_some_small_buffer.

To do this I created an instance array of checkboxes (did you know you could do that?). Here is what it looks like:

W_main Instance Variables

checkbox icbx_days[7]

The icbx_days array will hold the days of the week in their proper order. If today is Friday then icbx_days[1] will be the checkbox for cbx_Tuesday. We will handle that in the open event. Let's take a look at the open event, which is the core of this whole thing.

First we need an array that will be the checkboxes in the order in which they will eventually be needed. I named that lcbx.

We can find out the day of the week with the dayNumber function passing today() as an argument. The fourth element of icbx_days should always be today, so we start from there. We set the background color since we want it obvious that is today. After that we set the fourth element (middle) of the instance variable icbx_days to be the checkbox in the local array that is at the day number.

If this isn't clear, go to the listing and look at the four lines under the comment //Today is in the middle. That should make sense to you.

After that there is series of code segments where I decrement the li_index variable, loop it around if needed, then just set the checkbox in the local array to the instance variable. In essence I'm loading the instance array with the checkboxes in the order that I need to display.

You might want to look about halfway down these segments for the comment that says // Now Tomorrow. That's where I start loading the future days.

Finally there is a for-next loop that moves the checkboxes to the proper places.

It is Monday when I wrote this column so if you look at Figure 4 you will see the final result.

// Move the checkboxes to the proper sequence
int li_cbx_x_positions[7], li_index, li_y = 112
long ll_start, ll_delta, ll_count, ll_width

checkbox lcbx[]
lcbx = {cbx_sunday, cbx_monday, cbx_tuesday, cbx_wednesday, cbx_thursday, cbx_friday, cbx_saturday}

// Today is in the middle
li_index = dayNumber(today())
lcbx[li_index].backcolor = rgb(178, 34, 34)
lcbx[li_index].textcolor = rgb(255, 255, 255)

icbx_days[4] = lcbx[li_index]

// Let's do yesterday
li_index --
if li_index < 1 then li_index = 7
icbx_days[3] = lcbx[li_index]

// Now the day before yesterday
li_index --
if li_index < 1 then li_index = 7
icbx_days[2] = lcbx[li_index]

// Now the day before that
li_index --
if li_index < 1 then li_index = 7
icbx_days[1] = lcbx[li_index]

// Now tomorrow
li_index = dayNumber(today()) + 1
if li_index > 7 then li_index = 1
icbx_days[5] = lcbx[li_index]

// Now tomorrow
li_index ++
if li_index > 7 then li_index = 1
icbx_days[6] = lcbx[li_index]

// Now the last day
li_index ++
if li_index > 7 then li_index = 1
icbx_days[7] = lcbx[li_index]

//Now we move them to the right places
ll_delta = 30
ll_start = cbx_sunday.x
ll_width = cbx_wednesday.width

for ll_count = 1 to 7
icbx_days[ll_count].move(ll_start, li_y)
ll_start += icbx_days[ll_count].width + ll_delta

Download source code here.

More Stories By Richard (Rik) Brooks

Rik Brooks has been programming in PowerBuilder since the final beta release before version 1. He has authored or co-authored five books on PowerBuilder including “The Definitive DataWindow”. Currently he lives in Mississippi and works in Memphis, Tennessee.

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