I hope I am not labouring this issue too much. I appreciate the trouble Andrew has taken to explain this point but I fear that he has also missed the point. Andrew explains quite rightly what will happen on the CAD screen but he has not explained what will happen when it is printed out on paper. Taking Andrew's example sketch scaled 4:1 as the starting point, if it is printed out with QCad default settings for dimension measures, the character height will only be about O.6mm on the page which is unreadable, though it may look OK if you zoom in on the screen. If the dimension settings were scaled, they would be readable on the print, albeit somewhat crowded. Conversely, if QCad is allowed to scale the same entity to fit an A4 page, the character height will be about 15mm, assuming in both cases that a default dimension text height of 2.5mm is left in the preference box. Neither of these produce an acceptable scaled drawing, only the 1:1 drawing really works. When the image is scaled away from 1:1, it is still the case that something needs to be done with the text and dimension measures to produce a decent looking and readable drawing, as well as have something you can see on the screen. At either extreme, these parameters need to be brought back to some preferred size in the final print. I still maintain that this size on the final print should be the one chosen in the Drawing Preferences Dimensions box. Yes, there will be crowding of the dimension data if entities are scaled very small but, ultimately, that is a consequence of trying to put too much information onto a paper sheet which is too small whilst keeping it readable. Nonetheless, control of the final image should remain with the draughtsman who should able, based on the screen view, to decide whether to choose a smaller text size or leave things out and put them in a scrap view or in another drawing. As it stands, the QCad solution for addressing this requirement involves some inelegant manipulation of Dimension Preferences because the sizes which need to be set for the drawing attributes are non-intuitive and involve scaling the dimension preference data to suit the extents of the drawing.
Andrew quite rightly says that the extent of a drawing should be determined before work begins and the draughtsman should decide the scale but QCad does not provide the facility to set the scale at the outset. Even if the scale is set in the Print Preview box at the start of drawing, it does not have any functional effect during on the user interface with the application, only at print time. If QCad permitted definition of a scale in the Drawing Preferences dialogue, this information could be be used to scale the drawing attributes so that dimension data could be read on the screen and in print especially for entities which are considerably larger than the drawing sheet. However, the need to set a scale seems to contradict the usability philosophy of QCad. QCad invites the user to draw first and then scales the image to fit the printed page or allows the user to manipulate the extent of the drawing relative to the printer page in Print Preview mode. At this point a scale is established.
I think there is potentially a simple and neat solution to this problem. QCad should use the scale factor defined in the Print Preview to modify automatically, in background only, the drawing preference settings so that the drawing attributes for the printed page match those specified in the drawing settings. Once the user has defined the extent of their drawing relative to the print page, this would adjust drawing parameters to provide a readable drawing, avoid the non-intuitive manipulation of drawing settings and maintain the intuitive usability of QCad. It would also show, on screen, the consequences of any potential crowding of dimension data etc whilst the drawing is being created. If this idea should be adopted, could I take this suggestion one step further and propose that the scale setting dialogue box in the Print Preview mode view should be replicated in the Drawing Preferences Dimensions dialogue box, so that the user can, if desired set a scale at the outset of the drawing creation? At the very least it would be wonderful to have a dimension scaling facility as a configurable option in Application Preferences.
As an afterthought for readers of this topic, I would also point out that the overlapping of the dimension text and dimension lines shown in Andrew's scaled image has occurred because it was originally drawn at 1:1 scale and then scaled down. If the draughtsman had applied a scaling factor to the dimension measures before dimensioning had taken place, to suit the extent of the printed image, he would have seen the dimension text shown in larger size on screen and would have been able to place the dimension lines further apart from the start. Scaling of the dimension measures does not automatically cause crowding unless it is applied after dimensioning has taken place. This is further reason to facilitate setting up scaling of these measures before drawing starts.