bug(select): Options panel positioning does not work

[fkolar]

Reproduction

Steps to reproduce:

1. here is the repo to show the problem
   • npm install, ng serve
2. Once you open up browser scroll down so you force select to open towards up

3. select should open normally
4. scroll down in the option panel and select last item Tom1ato
5. Open up the select again and the overlay panel is completly off.
   

Expected Behavior

What behavior were you expecting to see?

I would like to maintain the behavior when you initially opened up the select. Overlay should stay on the same possition and scroll correctly to selected item

Actual Behavior

What behavior did you actually see?
Overlay jump all the way up, completly off from triggering select and Does not even scroll to selected item.

Environment

Angular CLI: 9.0.7
Node: 12.0.0
OS: darwin x64

Angular: 9.0.7
... animations, cli, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router
Ivy Workspace: Yes

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.900.7
@angular-devkit/build-angular     0.900.7
@angular-devkit/build-optimizer   0.900.7
@angular-devkit/build-webpack     0.900.7
@angular-devkit/core              9.0.7
@angular-devkit/schematics        9.0.7
@angular/cdk                      9.2.4
@angular/material                 9.2.4
@ngtools/webpack                  9.0.7
@schematics/angular               9.0.7
@schematics/update                0.900.7
rxjs                              6.5.5
typescript                        3.7.5
webpack                           4.41.2
    

[jelbourn]

@fkolar did you mean to include a reproduction here? If so, StackBlitz would be most useful. You can quickly create a StackBlitz from the MatSelect docs: https://material2-dev.firebaseapp.com/select

[fkolar]

Sorry. Getting old ;-) I though I included this link:

https://github.com/fkolar/matselecttest

[crisbeto]

Looks like an issue with the logic that tries to position the option over the trigger doesn't work correctly when it's close to the bottom of the screen and the active option is around the middle of the list.