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Why do I have problems with really big charts?


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Posted 16 August 2004 - 12:45 AM

Why do I have problems with really big charts?
Applies to: All products under Windows 95/98/ME (only)

Answer: The older operating systems listed above are not capable of handling some really large charts. Generally speaking, the maximum chart size under these operating systems is about 28 feet by 28 feet. A chart that is beyond those limits will open, but the far right or bottom of the chart will show lines flying off in the wrong direction, missing boxes, etc.

The exact maximum size depends on a number of factors, including your system configuration and the contents of the chart itself. At some point, however, the operating system (not the software) may run out of resources before it is able to finish displaying the chart. Note that the amount of memory (RAM) or hard disk space on your system cannot overcome this problem. It is a limitation of the operating system itself.

Technical explanation: Although Windows 95/98/ME are "32-bit" operating systems, they use a 16-bit Graphics Device Interface or GDI, which limits the x and y coordinate system for text and graphics to 32K. That is, drawing commands can address 32768 x 32768 dots or "logical units." A default installation of Windows 95/98/ME uses "Small Fonts" (under Windows Display Properties) and 96 dpi (dots per inch). That means that the operating system can address a drawing area of 32768 / 96 or 341.333 inches (28.4444 feet) square.

When Windows Display Properties are configured for "Large fonts," it supports 120 dpi and, using the same math as above, the effective maximum chart size is 22.75556 feet in both directions.

Even within the estimated maximum sizes above, the 16-bit GDI of those operating systems may trigger other resource limitations if your chart has an extremely large number of boxes, images, or other "objects."

Solutions:
  • If possible, use Windows NT, 2000, XP or later. These operating systems use a 32-bit GDI and have no practical limitation as to chart size.
  • Limit the overall size of your chart (smaller boxes or fewer generations, etc). Note that reducing the font size of data has the possible effect of reducing the height of the chart (by reducing word-wrap), but it will not affect the width of the chart because that is controlled by a specific chart configuration option.
  • Rearrange your chart. A top-to-bottom chart causes boxes in the same generation to be laid side-by-side, so the width (usually the longer edge) of those boxes add up quickly to produce a wide chart. The same chart aligned left-to-right will cause boxes in the same generation to be laid above and below one another, so that their heights (usually the shorter edges) add up to produce the height of the chart. The result is that the same data is displayed in a smaller space and the overall size of the chart is smaller.
  • Use "Small fonts" under Windows Properties (right-click on the Windows desktop, choose Properties, and select the Settings tab). Note that this is NOT the same thing as specifying smaller fonts for a particular chart.
  • The corruption that you see on a large chart is not saved within the chart file. Rather, it is a function of how your operating system reads it. You can therefore design and save a chart and (although you can't preview it all) send it to someone using a more modern operating system for printing. For instance, you can send it to Chartform Delivery, Wholly Genes' printing service which runs on operating systems that are not affected by this problem.
Other keywords: Visual Chartform




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