Repository: spyder-ide/spyder

Issue:
Selected figure thumbnail in Plots not highlighted in dark mode
In the dark mode when scrolling through the figures it is not very clear which is the currently shown figure, Whereas in the light mode there is a blue boundary surrounding the selected figure.

Drak Mode
![dark_plot](https://user-images.githubusercontent.com/22060413/65207582-efcbdb00-da89-11e9-8b0b-8ceaefd0af8d.gif)

Light Mode
![light_plot](https://user-images.githubusercontent.com/22060413/65207599-fce8ca00-da89-11e9-8702-02b39e9fb9cf.gif)


Is it possible to make a similar boundary with probably a different color than blue for Dark theme to clarify what is the currently displayed figure? and possibly also make the thickness of the boundary line higher

* Spyder version: Spyder 4.0.0.dev0 [a2d0dbcbd](https://github.com/spyder-ide/spyder/commit/a2d0dbcbd)
Python 3.7.3 64-bit | Qt 5.9.7 | PyQt5 5.9.2 | Windows 10

### Dependencies
<!--- Please go to the menu entry Help > Dependencies,
press the Copy to clipboard button and paste below --->

```
cloudpickle >=0.5.0          :  1.2.2 (OK)
pygments >=2.0               :  2.4.2 (OK)
qtconsole >=4.5.5            :  4.5.5 (OK)
nbconvert >=4.0              :  5.6.0 (OK)
sphinx >=0.6.6               :  2.2.0 (OK)
pylint >=0.25                :  2.3.1 (OK)
psutil >=0.3                 :  5.6.3 (OK)
qtawesome >=0.5.7            :  0.6.0 (OK)
qtpy >=1.5.0                 :  1.9.0 (OK)
pickleshare >=0.4            :  0.7.5 (OK)
zmq >=17                     :  18.1.0 (OK)
chardet >=2.0.0              :  3.0.4 (OK)
numpydoc >=0.6.0             :  0.9.1 (OK)
spyder_kernels >=1.5.0;<2.0.0:  1.5.0 (OK)
qdarkstyle >=2.7             :  2.7 (OK)
atomicwrites >=1.2.0         :  1.3.0 (OK)
diff_match_patch >=20181111  :  20181111 (OK)
watchdog                     :  None (OK)
keyring                      :  None (OK)
pexpect >=4.4.0              :  4.7.0 (OK)
pympler                      :  None (OK)
sympy >=0.7.3                :  None (NOK)
cython >=0.21                :  None (NOK)
IPython >=4.0                :  7.8.0 (OK)
matplotlib >=2.0.0           :  3.1.1 (OK)
pandas >=0.13.1              :  None (NOK)
numpy >=1.7                  :  1.15.4 (OK)
scipy >=0.17.0               :  None (NOK)
pyls >=0.28.2;<0.29.0        :  0.28.3 (OK)
rtree >=0.8.3                :  0.8.3 (OK)

```



Discussion:
Thoughts @jnsebgosselin ?
Not sure wither you agree on these changes. 
![image](https://user-images.githubusercontent.com/22060413/65213166-fadc3680-da9c-11e9-8edf-93100f498f73.png)

![light_plot2](https://user-images.githubusercontent.com/22060413/65213297-88b82180-da9d-11e9-9cb6-87bbaeba5834.gif)

![black_plot2](https://user-images.githubusercontent.com/22060413/65213302-8d7cd580-da9d-11e9-88c5-cd370cd67db1.gif)

But maybe there is a better way to get a different color (e.g. red) rather than hard coding it.

> Not sure wither you agree on these changes.

Thanks a lot @Khalilsqu for taking a look at this one! I think they are fine, so please create a PR for them.

Resolving patch:
diff --git a/spyder/plugins/plots/widgets/figurebrowser.py b/spyder/plugins/plots/widgets/figurebrowser.py
--- a/spyder/plugins/plots/widgets/figurebrowser.py
+++ b/spyder/plugins/plots/widgets/figurebrowser.py
@@ -913,8 +913,14 @@ def highlight_canvas(self, highlight):
         """
         colorname = self.canvas.palette().highlight().color().name()
         if highlight:
-            self.canvas.setStyleSheet(
-                    "FigureCanvas{border: 1px solid %s;}" % colorname)
+            # Highlighted figure is not clear in dark mode with blue color.
+            # See spyder-ide/spyder#10255.
+            if is_dark_interface():
+                self.canvas.setStyleSheet(
+                        "FigureCanvas{border: 2px solid %s;}" % "#148CD2")
+            else:
+                self.canvas.setStyleSheet(
+                        "FigureCanvas{border: 2px solid %s;}" % colorname)
         else:
             self.canvas.setStyleSheet("FigureCanvas{}")
 


Test patch: