### Display

By default trs80gp starts in authentic display mode. This mode looks most like the original TRS-80 display and scales very well to fit any window size. It is selected with `-va` or View → Authentic Display.

For a less realistic but still scalable display there is View → Sharp Display or the `-vs` flag. In this mode pixels are drawn as tiny rectangles in a single colour rather than the fuzzy dots that are brightest in the middle used in authentic mode.

Since the sharp display doesn't look as good at some scales due to poorer antialiasing there is View → Fixed Sharp Display or `-vi`. While the window can be resized in this mode the display will only use whole number scales (e.g., 1X, 2X, 3X, etc.) to make the display look as sharp as possible.

Finally there is View → Cheap Display or `-vh`. It will scale up in whole number jumps it always maintains a correspondence between TRS-80 pixels and PC display pixels even if the aspect ratio is not the same as the original TRS-80 display. The Model I mode is particularly distorted and the window size will change when a Model 4 switches between 80 and 64 character modes. This mode is mainly of benefit to PCs with small displays or less processing power. It is also useful for testing since the mapping from the resulting pixels to TRS-80 graphics is simpler.

While ignored in authentic mode, `-vN` can be used on the command line to start the emulator at a fixed display scale (e.g., `-v3` for 3X scaling). In any mode `-win WxH` can set the starting window size to W x H.

trs80gp can start in full screen mode (showing no menu bar, window borders or system elements) using `-vf` or `-win full`. Use the View → Fullscreen menu entry to switch to full screen mode at any time or toggle between fullscreen and windowed with the `Alt-Enter` keyboard shortcut. Or use the right-click context menu. Full screen mode is nice for those whose eyesight isn't what it used to be or if you want your PC to feel more like a real TRS-80 instead of an emulation.

The View → Controls dialog allows additional control over the display. There are sliders to adjust the brightness and contrast of the display much like the original TRS-80. It even permits adjustments that leave the display dimmed or brightened beyond readability.

The display colour can be changed from the usual bluish-white to any colour you like with quick presets for Green, Amber and white. Similarly the colour used to show beam conflicts (a programmer feature, more on that below) can also be changed from the default blue. Changes to colours become the default on a per-model basis. I personally like my Model 4 display green and amber for the Model 2. The `-vc` and `-vd` command line options can change the display colour without saving it as a default. Or they can specify the factory default by using `-` as the colour (e.g., `-vc -`).

Under Windows trs80gp remembers the display mode and window positions for each particular model. The windows can be set up just the way you like them and will be in those positions the next time you run. If you run more than one trs80gp emulator for a model at once the second and subsequent instances will have their own set of window positions and display settings. They will also indicate the instance as a `#2`, `#3`, etc. in the window title bar.

#### Beam Debug

View → Beam Debug (or `-bd`) turns on beam debug mode which is used to illustrate when the Z-80 and video circuitry conflict over access to display memory. When this happens on a real TRS-80 the video display will show short black streaks (or white in hires) instead of the actual data displayed. This was most prevalent on the Model I and was colloquially referred to as "screen hash" or "snow" or "raster lines". The Model 3 has this to a generally lesser extent. It should appear in Model 4 hires modes and on the Model 2 but, much to my shame, I have not written that emulation yet.

In "Beam Debug" mode these dropouts are instead coloured in blue to made them even more noticeable but yet show what would have been displayed had there been no conflict in shades of blue. This is very helpful for getting the timing right when development programs that write to the display with very precise timing to increase effective display resolution. For instance, see my bouncing ball demo. Beam debug mode reveals how it secretly writes to the display where it is already black so beam conflict remains hidden from view.

This mode also shows the V-Blank and H-Blank portions of the display as rectangular regions below and to the right of the usual display respectively. Z-80 access to video memory during those times will show up as beam conflicts even though there is no actual conflict. Instead they function as a sort of oscilloscope to show when the Z-80 is accessing video memory. H-Blank or "Horizontal Blank" is the short time when the CRT electron beam is moving from the end of a display line to the start of the next one. V-Blank or "Vertical Blank" is a longer interval when the beam is moving from the bottom of the display to the top.

Beam Debug is not supported by the authentic display mode so if activated it will automatically switch the TRS-80 to cheap display mode.