Old .qgs project causes GUI mess

[qgib]

Author Name: Mateusz Loskot - (Mateusz Loskot -)
Original Redmine Issue: 1081

Redmine category:project_loading/saving
Assignee: Tom Elwertowski

---

I've experienced strange behavior of latest QGIS 0.10.0 under Mac OS X 10.5. I have a .qgs project (old_postgis_project.qgs) composed with a few [[PostGIS]] layers. I created it using 0.9 version. I copied this project file to another computer without database used in the project definition and tried to open it with QGIS. Here are steps I took, with references to screenshots illustrating every stage.

1. Launched QGIS (1.png).

2. File -> Open Project -> old_postgis_project.qgs loaded. The screen 2.png shows error message I got after clicked Open button in file selection dialog.

3. I clicked OK on the message box and GUI got completely messed (3.png)

4. I resized the messed main Window to present the destruction better (4.png)

---

• old_postgis_project.qgs (Mateusz Loskot -)
• 1.png (Mateusz Loskot -)
• 2.png (Mateusz Loskot -)
• 3.png (Mateusz Loskot -)
• 4.png (Mateusz Loskot -)

[qgib]

Author Name: Tim Sutton (Tim Sutton)

---

Tom could you look at this?

Thanks

Tim

[qgib]

Author Name: Tom Elwertowski (Tom Elwertowski)

---

I consider the priority of this bug to be minor. Although it results in visual corruption, it does not cause a crash or corrupt data. Since the visual corruption is caused by attempting to open a project for which no layers are present, a workaround is to quit, restart and don't open the project again until the layers are available.

For qgis 1.0, I consider this bug 'wontfix.' The fix is to redesign the render code. This could be a task for the next major release (2.0) but not sooner.

This type of visual corruption occurs because Mac paint events are not interruptible. Interrupts are caused by calls to processEvents() inside paint events; removing them requires a redesign.

I suspect there are also Mac problems using a QGraphicsScene with an offscreen bitmap. Mac rendering has been unstable ever since QGraphicsScene came into use for map rendering. The conflict is that QGraphicsScene tries to do visual optimizations and qgis render code also tries to do visual optimizations. I recommend using either QGraphicsScene or an offscreen bitmap but not both. Mixing the two seems to confuse Qt/Mac.

One final comment. I encounter some sort of visual corruption almost every time I use qgis (on a Mac). Usually the window title, window controls and toolbar buttons get drawn inside the map canvas. Doing additional work redraws the items correctly. Doing yet more work causes more visual corruption again. The details of the corruption change with each Qt release but will continue until map rendering becomes Mac 'event safe.'

---

• resolution was changed from to wontfix
• status_id was changed from Open to Closed

[qgib]

Author Name: Mateusz Loskot - (Mateusz Loskot -)

---

Tom,

Thanks for the explanation. I agree with your decision.

[qgib]

Author Name: Anónimo (Anónimo)

---

Milestone Version 1.0.0 deleted