Bluee asked me to post a tutorial on how to get your game window to still fit fully in your screen even though it's outputting at the higher resolution that you told it to with SourceRes. Side effects include mouse detection being misaligned in-game (aka you can hardly use the mouse), horrible downscaling (very pixelated because it uses a nearest neighbor technique; you can see the before and after (native and shrunken w/ SourceRes, respectively) here and here. Those screenshots are simulated but it gets the point across; in practice it'll probably look even worse.

Anyway, you need to install GameCompanion from here. This utility is used for many other games in order to force a borderless window output mode. Essentially it strips the borders from a window and then stretches it with a form of overlay to fit across the screen. This will stretch with nearest neighbor techniques so if you output to a resolution that isn't your native res (usually lower, but in our case, higher), the result will look atrocious, as shown earlier. After installing GameCompanion, open it and find out what your "Manual FFMode" hotkey is. Mine is Ctrl+Enter, but I don't recall if this is the default. Anyway, start TF2 now with the "-windowed -insecure" parameters (additionally "-novid" or any other parameters, but do not use "-noborder", as I'm not sure how it behaves with GameCompanion). Once it's launched in a window, use SourceRes in the console to target the output resolution you want - for example, to make your game output at 4K, you'd enter "sr_forceres 3840 2160". Then, once it's adjusted your resolution, hit Ctrl+Enter (or whatever your hotkey is/was) while still in the console. Staying in the console is entirely optional, but is definitely more convenient as the "enter" key will probably trigger a menu button, and you'll want the console open afterward anyway. This should stretch your window to fill your primary monitor.

From here, you're pretty much done. You're viewing a downscaled version of the incredibly high res game now, but even though your view is downscaled, all images and videos will be rendered at the SourceRes resolution. You can close GameCompanion when you're done capturing. Enjoy!

EDIT: In order to reassure based on previous complaints, mouse tracking should only be broken for navigating menus and things of that nature. Rotating for thirdperson shots should be okay.

EDIT2, 10 months later: For those of you trying to get this to work, be sure that in GameCompanion's settings window, in the Options tab, you have FFMode set to Type2, not Type1. Be sure to restart both GameCompanion and TF2 fully once setting this option for it to take effect.

Also, are you taking map requests? ESEA is playing on cp_sunshine_rc1a this week, so I took an image for that map.

cp_sunshine_rc1a
scale: 10.00
pos_x: -10583
pos_y: 9169

oh god source for this masterpiece is going to be a thing get hype

I suggest putting it on something like Github so you can take pull requests that become official.

Developing an anchoring system wouldn't be hard. I've got a class coming up in a few minutes but when I get back I could even draw up some pseudocode that only contains if statements and definitions for values. I'd happily do the hard work for you if it meant this could be a thing.

Alternatively you could always just have offset from left, right, top, and bottom, and if top is defined, undefine bottom and use top, if the user then defines bottom, undefine top and use bottom, mirrored for left/right. Not sure if that'd be possible with event handlers but I'd assume it would be.

The issue isn't for offset from the top left, specifically. The issue lies in if you want it to be affixed to the bottom right. Let's say, I have a 1600x900 monitor (which I do) and I want the minimap size to be 2 (doubled) and affixed to the bottom right. I have the horizontal_pos set to 1300 and vertical_pos set to 542. For 1600x900, this looks fantastic. However, as soon as you want to give this to another user (1280x720 or 1920x1080), you need to recalculate everything, remembering the size and offsets from max. It's a pain and while you could do it manually with trial and error for smaller resolutions, it's near impossible for larger ones.

Raw pixel offsets with anchors is honestly the best solution. Every decent GUI framework out there, even WinForms, uses this method.

I think it would be totally acceptable to just disable it in third person as well if you can't find a proper workaround.

I'm going to be using this in all of my team's productions.

Feedback so far:
The health bar shouldn't appear for the player you're currently viewing if viewing that player from a first person cam. It flies all over the top of the screen depending on where they're looking. Not good.

The minimap shouldn't have "horizontal pos" and "vertical pos", it should use anchors and offsets. For example, four vars: "anchor_top 1", "anchor_bottom 0", "anchor_right 1", "anchor_left 0" would anchor it to the top right, and then "offset_x 50" would offset it 50 pixels from the right of the screen (to the left of the right side), and "offset_y 10" would offset it from the top that amount. Currently, in order to put the minimap in the bottom right, you need to know the exact resolution of your display in order to make it look decent at all. This means I can't share my exec with my co-caster running a different resolution unless I customize it specifically for him, and I can't because his resolution is above mine.

Other than that, fantastic work. Maybe some more customization options would be nice (change health bar's outline color?) but it's a fine piece of work.